Mayor Marion Barry took the first formal step of his reelection campaign yesterday when supporters announced formation of a 102-member campaign finance committee that hopes to raise $500,000 for the city's Sept. 14 Democratic primary.

The committee is headed by Delano E. Lewis, a vice president and lobbyist for the C&P Telephone Co. and a longtime friend of Barry. The members of the committee include a wide-ranging collection of bankers, businessmen, real estate developers, lawyers, hotel and restaurant owners and longtime personal friends and associates of the mayor.

Some of the members are major real estate developers and businessmen who are locked in a high-stakes fight before the city's Redevelopment Land Agency (RLA) for the right to build on the coveted 10-acre Portal site in Southwest Washington, the largest tract of undeveloped land in the core city.

Those members include Lewis, Conrad Cafritz, Roger Blount, Roy Littlejohn, John Clyburn and James Atkins. A decision on the property is expected next month.

The committee also includes several principal fund-raisers for former mayor Walter E. Washington and former City Council chairman Sterling Tucker, whom Barry defeated in the 1978 primary despite the fact that Washington and Tucker each raised more funds that Barry.

William B. Fitzgerald, president of Independence Federal Savings and Loan Association, is among them. Fitzgerald was a principal fund-raiser for Tucker in 1978, but has since grown closer to Barry. The mayor's wife Effi is on the board of Independence.

Charlotte Chapman, who was treasurer of Washington's 1978 campaign, lawyer Richard K. Lyon, who raised money for Washington in 1974 and 1978, and Theodore R. Hagans Jr., a developer who was with Washington through the primary but now has strong ties to Barry, are also members.

Councilmember Charlene Drew Jarvis (D-Ward 4), who is actively considering a race for mayor, said yesterday the list "is significant in the number of people who are not on it, who have decided to wait and make a more considered judgment."

Councilmembers John Ray (D-At Large), John A. Wilson (D-Ward 2) and Betty Ann Kane (D-At Large), who also are in various stages of running for mayor, could not be reached for comment yesterday.

The Barry list also includes lawyer R. Robert Linowes, former president of the Greater Washington Board of Trade, Don Bruce, the owner of several gay bars; Vi Curtis Hinton, Washington coordinator of the NAACP Legal Defense Fund; Calvin W. Rolark, publisher of the Washington Informer newspaper; and Joe Schuble, president of Dreyfuss Brothers. CAPTION: Picture, MAYOR MARION BARRY. . .$500,000 for the primary.