President Reagan intends to nominate Faith Ryan Whittlesey, the White House director of public liaison, to be ambassador to Switzerland, continuing a string of departures by conservatives from the White House, officials said yesterday.

Whittlesey, 45, the most senior woman on the White House staff, has been assistant to the president for public liaison since March 1983. She has been in charge of explaining Reagan's policies to outside groups and bringing them to the White House to meet with the president. She served as ambassador to Switzerland from 1981 to 1983.

Considered one of the most ardent conservatives in the White House, Whittlesey had her share of conflicts with some of Reagan's more pragmatic advisers. Officials said other conservatives had urged her to remain at the White House during Reagan's second term, particularly because presidential counselor Edwin Meese III has been nominated to become attorney general and Secretary of the Interior William P. Clark is resigning.

Both men are considered conservative voices in Reagan's high command.

Whittlesey would not comment yesterday on her pending ambassadorial nomination, which must go through several clearance procedures. But officials said it is likely to come through in March or April. She would replace Ambassador John Davis Lodge.

It could not be learned whether Lodge, a longtime Reagan supporter, would get another assignment.

Whittlesey touched off a controversy in 1983 when she suggested at a White House meeting that the "gender gap" was exaggerated at a time when many of the president's aides viewed it as a major political problem.

Yesterday, Whittlesey said she felt "vindicated" by Reagan's landslide reelection victory. "The polls and the results indicate I was closer to the truth," she said.