North Korean President Kim Il Sung's son emerged from obscurity in Pyongyang today, adding new weight to speculation he will be designated the country's future ruler in what would be the communist world's first dynastic succession.

The son, Kim Chong Il, was listed fifth in prominence among members of a steering committee of the North Korean Workers Party congress that opened in Pyongyang this morning, according to news reports and monitors here.

It was the first time the son's name has appeared in print, although he is believed to hold a high party position. The only persons ranked ahead of him were his father and three other aging party leaders and office-holders.

North-Korean sources in Tokyo who monitored Pyongyang broadcasts said the son also had appeared at the congress and they said it was his first public appearance in an audience with foreigners. The report could not be confirmed.

There have been rumors for months that the 68-year-old president, who has ruled for 35 years, would unveil his son as his successor before an audience of world communist leaders. Although no such announcement emerged today, analysts here regarded the appearance of his name along with the party's top leadership as evidence he is being brought forward as the potential ruler.

The first party congress since 1970 was opened before an audience that included delegates from 118 countries and about 3,000 members of the party's rank and file.

Among them were a member of the Soviet Politburo, V. V. Grishin, and a vice chairman of the Central Committee of China's Communist Party, Li Xiannian, according to accounts monitored here from the official Korean Central News Agency. The agency said both were welcomed warmly at the Pyongyang airport in separate greetings.

In past years, North Korea has received aid and support from both big Communist rivals but recently it has grown closer to the Chinese. Its relations with Moscow has progressively cooled since the mid-1970s, in the view of Western analysts.

Kim Il Sung's opening remarks to the congress seemed to stress his country's independence from foreign countries.

He stressed North Korea is a "powerful social state independent in politics, self-supporting in economy, and self-reliant in national defense," according to one monitoring source.

The president devoted much of his lengthy opening speech to his nation's economy, claiming it had made great strides in modernization and growth since the last party congress.

He boasted of attaining an average annual growth rate of 15.9 percent in industrial production during the 1970s and listed major gains in electricity generation, railroad construction, and agricultural production.

There were no reports of any new initiative in the off-and-on negotiations with South Korea on reunifying the country, although the president hinted at some new program during the congress, which lasts for five days. He said the congress will put forward "a new-struggle program to achieve the independent, peaceful reunification of the country."

The North recently halted a series of working-level meetings in the border village of Panmunjom and severed a telephone hot line that linked Pyongyang and Seoul. It also has stepped up its harsh propaganda attacks headed by former Gen. Hun Doo Hwan, calling him the head of a "fascist clinque."

The succession question preoccupied most foreign observers of the party congress who have long taken it for granted Kim Il Sung will place his son in a position of top power someday. Some of the analysts believe Kim Chong Il was designated the successor several years ago and that opinion is shared by North Korean sources in Tokyo.

For a while, analysts believed the president was dying of cancer, citing a large growth on the right side of his neck. But intelligence sources have now concluded the growth is nonmalignant and recent visitors to Pyongyang, including U. S. Rep. Stephen Solarz (D-N.Y.), have said he appears to be in excellent health.

Very little is known abroad of politics in the North Korean capital because few outsiders are permitted to visit it from the noncommunist world and most intelligence consists of rumors and odd bits of information impossible to corroborate.

Almost nothing is known for certain about the son. Until today, he was referred to in the party press only by a kind of code name of "the party center," or sometimes the "glorious party center."

Analysts say the activities of "party center" have been featured prominently in the press this year. Reports of his visits to industrial plants and farms have increased in number.

The young Kim is believed to be 39 or 40 years old, a son of the president by his first wife, who died in 1949. He is thought to have been born in Siberia, where his family was in exile, and educated both in China and East Germany.

He apparently has held a variety of important positions and North Korean sources say he most recently has been in charge of moderization of the economy and technological renovation. The son also has directed cultural moves recently and is known to have produced at least two movies in the past year, both of them glorifying Korean historical figures.

Many reports have it that young Kim was in part responsible for the brutal axe murders of two American servicemen at the Demilitarized Zone in 1976. Some analysts suggest he was blamed for endangering his country by exposing it to a potential U.S. counter move and was forced to disappear from public life for a while.

There is no consensus of what young Kim's succession would mean for the future. North Korean sources have described him as a vervent nationalist who frequently stresses the importance of "Korean character" instead of socialism as the key to his country's development.

South Koreans usually portray him as a dangerous figure who would show less restraint than his father in military adventures, but his opinions are based largely on guesswork. South Korea's ambassador-at-large, Hahm Pyong Choon, told reporters here this week that the son might try to prove himself as a worthy successor by attempting to unify the country by force.

"The son will have a compulsion to prove himself by achieving something his father did not," Hahm said.