Fairfax County Supervisor John P. Shacochis, a Republican representing the county's affluent Dranesville District, announced yesterday he will not seek reelection this fall.

The announcement by the 64-year-old, one-term supervisor was a surprise. As recently as last week he was wearing a "Shacochis for Supervisor" button in his lapel.

Shacochis joined two other members of the nine-member County Board who have decided against seeking reelection, saying they want to see more of their families.

Shacochis, a retired management engineer for the Bureau of Naval Personnel, sobbed onpenly yesterday in the board room in Fairfax City when he attempted to read a statement explaining his decision against running again for public office. The statement then was read by Supervisor Alan H. Magazine (D-Mason), who also has decided against seeking reelection.

"Quite simply I want to spend the remainder of my life as a private citizen, enjoying my family and my friends. I have grandchildren who hardly know me, and I cannot get to see them when I want to," the statement said.

Shacochis said he wants to spend his "golden years" with his wife Helen and visit his four children who now live across the country.

The silver-haired supervisor, who has become known on the board for his frequently loud voice in support of less government involvement in the lives of Fairfax citizens, also said he was getting out of local government because he does not like what he's seen of it lately.

"The principles of 'representative government' are being slowly eroded away. Under the guise of 'citizen participation,' small vocal groups are forcing elected officials into decisions which they know in their hearts are not representative of the will of the majority," the supervisor's statement said.

Shacochis, who lives in McLean, is the only one of the three retiring supervisors who does not have a fulltime job in addition to his duties as supervisor. The other two, Magazine and Warren I. Cikins (D-Mount Vernon) both have professional jobs that they say suffer because of the demands of being supervisors.

Both Magazine and Cikins, who announced their decision against seeking reelection earlier this year, have said it is exceedingly difficult to mantain a marriage, a family, a full-time job and put in the 40 to 80 hours necessary to perform the duties of a county supervisor. Shacochis, had he chosen to run for reelection, would have faced strong Democratic opposition from Maya Huber, who has strong party backing and who is an active member of the Fairfax County Federation of Citizens Associations.