Virginia's Republican state chairman, George N. McMath, is expected to resign his party post today amid reports that he is suffering from emotional and physical stress.

The 46-year-old party official, who yesterday confirmed published reports that he is considering resigning, said he would make final decision shortly after discussing the matter with state Republican leaders.

A source said late yesterday that personal pressures are forcing McMath's resignation and that he would "probably" step down today, citing health and emotional problems.

In a statement issued from party headquarters in Richmond, McMath, an Eastern Shore newspaper publisher, said he had "devoted nearly five years to the party and perhaps now would be a good time to turn this job over to someone else and devote more time to my family and business."

A former Democratic member of the House of Delegates, McMath switched parties in 1972 and has been GOP state chairman since 1974.

McMath had been expected to seek the Republican nomination for the state Senate seat now held by Sen. William E. Fears (D-Accomack). But he surprised many supporters last month by forgoing that race in the face of what he said were party and business responsibilities.

The announcement that McMath may relinquish his party post came after a Richmond newspaper reported yesterday that the Republican chairman was considering resigning. The article, citing unnamed sources, said McMath was thinking of stepping down because of emotional and physical stress brought on, in part, by the job.

McMath was hospitalized in the last month for old back problems he said "were flaring up recently," and which had required surgery more than a year ago for a ruptured disc.

Having expanded his newspaper properties from 12 to 17 in the last year-and-a-half, McMath said his increased business demands were conflicting with the 50 to 60 hours a week.

A GOP spokesman, Richard Lobb, said McMath would finally decide on whether to remain in the post before Republican Gov. John N. Dalton returns from a trade promotion tour in the Far East. Dalton is due home in June.

Under party rules, McMath's official resignation would have to be presented at a meeting of the Republican State Central Committee, would could not be held until next week. Or he could wait for the party's first off-year convention in Roanoke late next month and let delegates choose his successor.

McMath, the father of two teen-age daughters, announced two years ago that he was going to step down as party chairman, then changed his mind and stayed on, according to Lobb. CAPTION: Picture, Skier Suzy Chaffee helps HEW Secretary Joseph Califano put on his track shoes at an HEW-sponsored health fair being held through tomorrow on the Mall. The fair highlights healthful living. By James A. Parcell-The Washington Post