Northern Virginia Republican Rep. Frank Wolf opened his campaign for a second term last night, saying he is proud of his record and claiming credit for helping to control government spending, lifting the pay cap for top federal workers and limiting the number of flights into National Airport.

In a speech to about 550 people at the Dunn Loring fire station in Fairfax County, Wolf said he plans to campaign on his record and warned that he expects to face a "well-organized and well-financed" Democrat backed by organizations "that are most anxious to return our government to the way it was in the 60s and 70s."

Two Democrats are seeking their party's nomination -- Ira Lechner, an Arlington attorney, and Ted McLaughlin, a McLean media consultant. The 43-year-old Wolf was referring to Lechner, who has a liberal reputation and is favored to be the Democratic nominee from the 10th District, which encompasses Arlington and Loudoun counties and the northern half of Fairfax County.

Lechner, vice chairman of the state Democratic Party, has called Wolf a "Republican rubber stamp" who has "broken his campaign promises and voted for the entire economic package" of President Reagan. Those policies, Lechner has said, have hurt Wolf's constituents, 30 percent of whom are federal employes.

Both Republican and Democratic strategists say Wolf's record and the state of the economy are likely to emerge as key issues in the race, which is being monitored as an indication of the popularity of the current administration. Wolf is one of 52 GOP freshman who in 1980 swept into office on the coattails of Ronald Reagan.

Wolf declared: "In 1980 we asked voters for an opportunity to change the mainstream in Congress, to build a new mainstream, a new nucleus that was committed to controlling spending, lowering taxes and strengthening our national defense. I am proud to have worked and to have been part of that nucleus."

In recent months Wolf, a former baby food lobbyist who defeated Rep. Joseph L. Fisher in 1980, has tried hard to balance his enthusiastic support for the administration's policies and his votes in favor of many of the budget cuts with the desires of federal workers, some of whom have lost their jobs as a result of those cuts.

In the speech he stressed his role in lifting the pay cap for top federal officials and the day-long job fair he sponsored last Saturday at a Falls Church junior high school.

He told about 150 job-seekers at that fair that, "having been out of work myself, I know how very difficult the job search can be." He said he opposed reductions in force and favored attrition as a means of reducing the size of the federal work force.