Buoyed by the purchase of more than 100 tickets to a $500-a-plate luncheon, Marion Barry, the Democratic nominee for mayor of the District of Columbia, has raised five times as much money as his Republican opponent in the last two weeks, according to campagin finance reports.

In a statement filed Tuesday with the D.C. Board of Elections and Ethics, Barry reported receiving $64,998 since the last reports were filed Oct. 10, bringing to $361,058 the amount he has raised since declaring his candidacy in January.

Arthur A. Fletcher, the Republican nominee, has reported raising $40,979, including $12,533 since the Oct. 10 statements were filed.

Because he has not succeeded in raising enough money, Fletcher, a political newcomer to the city, has been unable to develop a media campaign to promote his candidacy.

Fletcher received still another apparent setback yesterday when the Taxicab Industry Group, which had strongly supported Mayor Walter E. Washington in last month's Democratic primary, decided to support Barry in the general election. Both Fletcher and Barry had sought the backing of the group, which claims to represent about 10,000 drivers and 60 companies in the city.

William J. Wright, chairman of the taxi group, said, " The men thought that Mr. Barry had experience with the City Council and was more experienced with local problems. Even though everyone didnot agree with everything he has done, people felt he would be best equipped to get along with a Democratic City Council.

Barry is an at-large member of the City Council, former D.C. Board of Education president and codirector of Pride Inc., a self-help group. Fletcher, a labor management consultant who was an assistant secretary of labor in the Nixon administration, has lived in the District only since 1975. He is running for office here for the first time.

Wright said the drivers, who distributed literature and ferried voters to the polls for Washington, will contribute " a small amount " to Barry's campaign. " We spent most of our money on Washington, " he said. Later this week, Wright said, the drivers will discuss with Barry what they can do for him in the Nov. 7 general election.

For the first time since he announced his bid for office, Barry's campaign report included dozens of contributions of $500 and $1,000 instead of the small donations he had received during the primary campaign, when most businessman favored Tucker and Washington.

Among those making contributions of $500 or more to Barry, apparently for the Oct. 10 fund-raiser, were Parking Management Inc. and its general manager, John W. Lyon, Oliver T. Carr Management Co., Julia M. Walsh & Sons Inc. (which gave $2,000), John W. Stadler of National Permanent Savings - Loan Assoication and James L. Harris, president of Washington Federal Savings and Loan Assoication, who told a reporter earlier that the had sold 22 tickers for the affair.

Most of the large contributions Barry received came from persons identified as builders, real estate firms, restaurants, liquor dealers and parking firms.