President Reagan met with the wife of imprisoned Soviet Jewish dissident Anatoly Scharansky in the Oval Office yesterday and promised to do all he can to help her husband.

"The president expressed deep sympathy for the persecuted Jewish and other religious communities in the Soviet Union as well as the plight of Mrs. Scharansky's husband and promised to do all in his power to alleviate the situation," deputy White House press secretary Larry Speakes said.

Speakes said U.S. officials will discuss Scharansky's case with Soviet officials, but he delcined to be specific about what Reagan will do to help the dissident, in his fifth year of a 13-year sentence.

"This is a time for quiet diplomatacy," Speakes said.

"I don't know how the president is going to act, but I trust him," Mrs. Scharansky told a press conference yesterday after the hastily arranged 30-minute meeting she and Losif Mendelevich, a Jewish dissident released from a Soviet prison three months ago after serving 11 years, had with Reagan.

She said the president had made no promises of specific actions he would take to aid her husband.

It was Reagan's first meeting with members of the Soviet dissident movement. The decision that he would meet them was made Wednesday afternoon, Speakes said. However, the dissidents were not told until the last minute that they would see the president.

Avital Scharansky and Mendelevich, who had met earlier with Secretary of State Alexander M. Haig, Jr., Vice Preisent Bush and National Security Adviser Richard V. Allen, had another meeting with Allan scheduled for yesterday morning. After they arrived in Allen's West Wing basement office, they were told that Reagan would recieve them in the Oval Office.

Mrs. Scharansky came to the United States several weeks ago after receiving word from her mother-in-law that her husband is suffering serious health problems in the labor camp where he is imprisoned.

Scharansky is losing his sight and memory and is down to 91 pounds, she told reporters en route to the United States from her home in Israel. She came to the United States to launch a campaign with the aid of National Conference on Soviet Jewry to attract public and government attention to Scharansky's case.

The White House did not announce Reagan's meeting with Mrs. Scharansky and Mendelevich until two hours after it had taken place because, Speakes said, the president thought the meeting should take place "without the spotlight of press and public attention."

"I think he understands the emergency situation," Mrs. Scharansky said of Reagan. "I think he understands that the life of my husband is in danger."

She said she found Reagan "very warm."

Mendelevich, who was in the same prison with Scharansky from 1978 to 1980, said Reagan was "very impressive."

Mendelevich, 34, was mildly critical of Carter administration efforts in behalf of Soviet dissidents. "I don't think it was very successful," he said of former president Carter's policy.

He refused to compare the Reagan policy, telling reporters: "I would like to judge according to the results."

Bush, White House chief of staff James A. Baker III, Allen, National Security Council staff Soviet specialist Richard Pipes and Jack Stein, White House liaison man to the jewish community, participated in the meeting with Reagan.

At her press conference, Mrs. Scharansky was asked whether her meeting had made her more hopeful.

"Yes," she replied in a quiet voice.