A one-time street preacher who last month turned down a national office in his church because he declined to uproot his family was elected bishop yesterday of the Washington Metropolitan Synod of the Evangelical Lutheran Church in America.

Delegates to the constituting convention of the newly merged church chose the Rev. Harold Jansen, 57, of Fairfax as bishop.

The Evangelical Lutheran Church in America (ELCA) was created nationally last month by merger of the Lutheran Church in America (LCA), the American Lutheran Church (ALC) and the Association of Evangelical Lutheran Churches (AELC).

Jansen, since 1979 the bishop of the Eastern District of the ALC, was elected on the fifth ballot, defeating the Rev. Charles Bergstrom 176 to 98, from a field that originally encompassed 35 candidates. Bergstrom is an LCA pastor who has directed the inter-Lutheran Office of Governmental Affairs.

The major focus of the local synod's two-day meeting, which climaxes with a liturgical celebration at the Washington Cathedral at 3 p.m. today, was the meshing of denominational machinery from three denominations and four former jurisdictions (churches from two previous LCA units were involved) into the new synod.

The new synod includes 36,176 baptized members from 72 congregations in the District of Columbia; Charles, Calvert, Montgomery, Prince George's and St. Mary's counties in Maryland, and Arlington, Fairfax, Loudoun, Prince William counties and Falls Church, Fairfax City and Alexandria in Virginia.

Adoption of a constitution and by-laws, and the election of scores of clergy and lay persons to operate more than a dozen committees and councils, filled most of the sessions held at George Washington University's Marvin Center.

Convention rules calling for special efforts to assure representation of women and ethnic minorities in policy-making posts worked so well that at one point the nominating committee's spokesman reported: "We've met the principle of inclusiveness, but we appear to be radically short of white males."

The one program item that drew heated discussion was a proposed "manifesto," detailing the mission of the new synod.

The stiffest opposition was voiced over a paragraph pledging area Lutherans to "overcome the prejudices of race, economic status, gender and sexual orientation that separate us from one another . . . . "

" 'Sexual orientation' raises the question of the permissive life style," said the Rev. Leroy Beutel of Arlington. Beutel and lay leaders of Faith Lutheran Church had sent a letter to all delegates before the convention charging that the wording of the proposed manifesto opened the door to "all possible sexual expressions imaginable, i.e., pornography, pedophilia, sodomy, homosexuality . . . ."

The majority of the delegates rejected efforts to delete that phrase and to send the manifesto to a study committee. The manifesto was adopted overwhelmingly.

Jansen, who began his career as a youth worker and street preacher in Brooklyn, N.Y., last month, withdrew from the race for secretary of the national church, which has headquarters in Chicago.