State Del. Robert L. Thoburn, a conservative Republican from Fairfax County, said yesterday he will run for the Republican nomination for Congress in Northern Virginia's 8th District.

Thoburn joins two other announced GOP candidates, Fairfax County Board of Supervisors Chairman John F. Herrity and Del. Robert E. Harris (R-Fairfax), in a primary race for the opportunity to challenge two-term Democratic incumbent Herbert E. Harris II.

An ordained Presbyterian minister and headmaster of the Fairfax Christian School, Thorburn, 48, says he is a politician who does not care if his views "are good politics or not."

He is a staunch opponent of the proposed Equal Rights Amendent which he says would give the federal government too much control over the family.

He advocates of the death penalty for murder and rape, favors keeping of the Panama Canal and urges government spending on the B-1 bomber and the neutron bomb.

Thoburn was narrowly defeated in the 1976 congressional primary by former Del. James Tate.In that election Thoburn carried Fairfax County and lost the Republican nomination by 143 votes. The 8th District includes Alexandria, southern Fairfax County, all of Prince William County and part of Stafford County.

In his first year as a delegate to the General Assembly in Richmond, Thoburn authored two bills. One would have required all local refernedums be held at the same time as general electins, and the second would have mandated a statewide advisory referendum on ERA. Neither bill got out of committee.

Thoburn sponsored two resolutions that were not approved. One called on the Congress to protect the "right to life" and the second denounced a proposed economic boycott by women's organizations protesting the failure of the Virginia legislature to approve ERA.

Thoburn was one of two Northern Virginia legislators to vote against the proposed one-cent increase in the sales tax, which would have been used to pay for Metrorail operating expenses (Robert Harris also voted against the plan.) Thorburn called his vote against the tax his "most signficant" action in Richmond. He said the tax would have hurt lower income people.

Del. Vincent F. Callahan Jr. (R-Fairfax), who sat near Thoburn in the General Assembly, said Thoburn is a "very sincere" legislator who is "a welcome relief" from politics as usual in Richmond. Gladys B. Keating (D-Fairfax) said Thoburn "is a person who sticks to his principles come hell or hight water."

The Republican primary is scheduled for June 13. Thoburn said he plans to attack Rep. Harris on "pocketbook issues" in the primary campaign and ignore his Republican opponents.