Sydney Buchanan Sullivan Walling, 73, an author and past member of the Board of the Washington Home who was a longtime Washington resident before moving to Randolph Center, Vt., in 1974, died of cancer Nov. 28 in her home there.

Mrs. Walling was born in New York City and moved to Washington when she was about 10 years old. Her father, Mark Sullivan Sr., had come to this city to work. He was an editor of the old Collier's magazine and a columnist with the old New York Herald Tribune.

After graduating from Bryn Mawr College in 1931, Mrs. Walling wrote short stories. They were published, under pen names, in magazines that included McCall's and the Saturday Evening Post.

She married Jameson Parker, a State Department official, in the early 1930s, and lived for a time in Baltimore and accompanied him to assignments in Europe. They returned to Washington in 1965, when he was named director of Gunston Hall, the historic home of George Mason. Mr. Parker died in 1972.

Two years later, she married L. Metcalfe Walling and moved to Vermont.

Mrs. Walling was a member of the National Society of Colonial Dames.

In addition to her husband, of Randolph Center, Mrs. Walling's survivors include two children by her first marriage, Jameson Parker of Hollywood, Calif., and Judith Parker of Philadelphia; a brother, Mark Sullivan Jr. of Washington; a sister, Narcissa Siechrist of Randolph, Vt., and four grandchildren.