Susan Porter Rose, appointments secretary to first ladies Pat Nixon and Betty Ford, will become chief of staff to Barbara Bush on Jan. 20, a spokesman for Vice President-elect George Bush confirmed yesterday.

Two other appointments to Mrs. Bush's staff include Laurie Green Firestone, as social assistant, and Becky Smith Brady, as personal assistant.

Rose, 39, currently on the staff of the assistant attorney general for administration at the Department of Justice, has known Mrs. Bush since Mrs. Bush was a surrogate for then-President Richard Nixon in the 1972 presidential campaign.

"Barbara remembered how efficient and professional Susan was," said Peter Teeley, press secretary to George Bush.

In defining her duties later, Rose said she expects to cover a broad range of activities, from working with the press and with Mrs. Bush's schedule to helping on her special projects and with official entertaining at the Vice President's House.

"Being a small staff," said Rose, "I expect we will help each other with everything."

She said no decision has been reached on her salary. Bess Abell, staff director to Joan Mondale, receives $50,000 annually.

Rose came to Washington in 1971 from Mount Holyoke College where she was assistant director of admissions. Before that, she served as assistant dean at George School in New Town, Pa. A native of Cincinnati, she grew up in Indiana where she earned a master of arts degree at Indiana State University.

In January, she married Washington attorney Jonathan Chapman Rose, an Army intelligence officer assigned to the White House in 1969 at the request of then-President Nixon. After returning to civilian status, Rose was named special assistant to the president and was general counsel to the counsel on international economic policy. His father was assistant Treasury secretary and undersecretary of the Treasury during the Eisenhower administration.

Socialite Laurie Firestone, 41, is married to Kimball C. Firestone, grandson of the founder of the Firestone Tire and Rubber Co. Kimball Firestone served as vice president of the family company for three years but resigned in 1976. The Firestones live in Potomac.