Greek heiress Christina Onassis' plans to marry a former Soviet shipping official in Moscow today have caused consternation among some shipping analysts here and anguish with her family.

But Onnassis' marriage to Sergei Kauzov is not expected to change the way the family's $500 million shipping, banking and industrial conglomerate is run.

The concern over the marriage is based more on the anomaly of a well-known, wealthy capitalist marrying a Soviet Communist Party member than on any good evidence that themarriage will effect the operations of the Onassis business.

Onassis told reporters in Moscow that the family business will continue to be handled in the West by associates of her father, the late Aristotle Onassis.

"There will not be one single change," she said. "All the speculation in foreign publications that the headquarters will be moved to Moscow is completely wrong."

Aristotle Onassis, who died in 1975, left a hand written will that turned over to his daughter nearly half his fortune and a significant voice in the control of the financial empire.

Family friends and business associates say Christina Onassis has proven to be fiercely independent and strong-willed.They said they doubted that her husband could influence her business decisions.

Some shipping authorities and government officials here dismissed the idea that her marriage to Kauzov might have any implications for the future of the Onassis business interests.

Nonetheless, the marriage is known to have caused deep anguish among Onassis family members, who at first refused to believe reports of the engagements and then sent an emissary to Moscow to try to talk her out of it.

"This is a disaster that has befallen us," one family member in Athens said of the engagement. A source close to the family business speculated that Onassis' decision to marry Kauzov may have been motivated by a belief that he could help her manage the family enterprises.

Since the rumors of marriage began late in June, the Onassis family has remained, for the most part, unapproachable, and when contacted they have refused to discuss the engagement. Onassis persistently denied the report at first, once telling a reporter. "What the hell you are talking about - me, marrying a Russian?"

Kauzov's mother in Moscow was the first to confirm the engagement, saying, "Yes, they are getting married. Isn't it such a nice thing to see two people in love?"

The news caused a sensation in Greece, where people of all economic levels and political persuasion - except perhaps Marxists - long regarded Aristotle Onassis as a folk hero of wealth, his name synonymous with that of Rockfeller and Rothschild.

Reports of Kauzov's apparent ease of movement through international business circles in the West led some to conclude that he may have connections with the KGB, the Soviet secret police. Some followers of the family enterprises began suggesting privately that the burgeoning Soviet merchant fleet - which becoming active in the depressed international shipping industry - somehow would benefit from the Onassis-Kauzov marriage.

Sources in the industry and close to the family point to persuasive evidence, however, that the marriage will have little effect on the Onassis business.

They note that Soviet laws allows a husband or wife independent ownership of property, and that Onassis reportedly has obtained a Soviet residency visa that will allow her to travel freely outside the Soviet Union.

IF she chooses, the sources said, she could remain active by periodically traveling to the Monte Carlo, Paris and New York headquarters of Olympus Maritime S.A., the Onassis' 40-vessel holding company, and the dozens of interlocking corporations throughout the world.

Family friends and business associates note that upon her father's death, Christina Onassis asserted her claim to 47.5 percent of the holdings, and immediately made it known she intended to actively manage the business.

A year after Aristotle Onassis' death, when some of the older directors sought to diversify and funnel capital away from costly oil tankers, Olympus Maritime lost a supertanker during its maiden voyage. The accident seemed to reinforce the director's decision, but Onassis reportedly insisted that the corporation purchase a similiar vessel for $27 million. Since then she has replaced 10 older vessels in a successful move to update the fleet.

She also replaced some of the older directors of the business and recruited an American, Louis Andersen, formerly with Exxon Corp. as general manager of the enterprises.

Business associates say that while Onassis is aggressively independent about her role in the company, she still regularly consults her father's trusted advisors.

"It is inconceivable that she could be influenced by anybody to do something that was in conflict with her intentions," said a family associate.

The government of Greece, so far, has shown little sign of wanting to become involved in the matter.

The director-general of the Maritime Ministry, Paul Sarlis, said in an interview in Piraeus: "We simply have taken due note of the reports. We consider this strictly private, outside the ministry's affairs.It is a matter of which the ministry does not concern itself.

"It is a love affair," he said, adding that almost all of Olympus' vessels bear foreign flags and are owned by foreign companies, although controlled by the Onassis empire.

A private shipping industry analyst here observed that the income produced by the shipping branch of the Onassis holdings, for the most part, is tied up in the Alexander Onassis Foundation, named for Christina's brother, who was killed in an airplane crash in 1973.

"It is not really a Greek company, in a sense," the analyst said of Olympus Maritime. "Its ownership is all over the world."

Christina Onassis still owns the island of Skorpios, where her father and brother were buried, but she recently transferred the lavish yacht "Christina," complete with its art treasures, to the government for use by heads of state.

Onassis reportedly has not been in Greece since last summer, when she vacationed at her summer villa in Glyfada, which she is said to be trying to sell. As her business activities abroad increase, her links to Greece are disminishing, according to associates.

Athenians, so far, have shown more interest in the prospects of a happy marriage than in the political implications for Olympus Maritime, largely because of Onassis' 27 years of personal difficulties - including the deaths of several relatives and two unhappy marriages.

She met Kauzov, 37, two years ago in Paris when the Soviet Union was buying grain from the United States and Canada and some shipments were to be made aboard U.S. vessels. Since much of the Onassis fleet is either registered or owned in the United States, Onassis negotiated a contract with Kauzov, who had been sent to Paris as a representative of Sovfracht, the Soviet shipping charter agency.

Kauzov is said to have been recalled to Moscow shortly after the meeting. He filed for a divorce from his wife, a cellist, gave up custoday of their nine-year-old daughter and moved into his mother's two-room apartment. He reportedly resigned from Sovfracht and began teaching English in Moscow. When his divorce became final , he is said to have sent for Onassis to join him.

Constantine Gratsos, the 76-year-old director of the Onassis' Far East and American business interests, flew to Moscow in mid-July totry to talk Onassis out of marrying Kauzov. He returneda few days later and is said to have told family members that Onassis intended to go through with the marriage.