D.C. City Council Chairman Arrington Dixon yesterday proposed the creation of a new Department of Economic Development and more promotion of tourism among blacks as part of a plan to help bolster the city's economy.

Dixon, who is running for reelection, said his proposals would help "insulate the District from the ravages of Reaganomics," including cutbacks in the federal government's work force and programs.

School board member Barbara Lett Simmons, seeking the Democratic nomination for an at-large seat on the council, also proposed an economic development plan yesterday as candidates in next week's primary elections marked Labor Day with appearances at picnics, block parties and a special Labor Day mass.

Simmons suggested creating a semipublic Economic Development Authority that would have broad powers to issue bonds, condemn land, operate commercial or industrial properties in cooperation with private firms and grant tax incentives and mortgage deferrals to struggling businesses.

She said the city should also develop a long-term jobs program that the city's public schools could use to plan curriculums.

"Our own unemployment lines are swelled not only with the unskilled, but with the scientist, the engineer, the teacher, and the social worker," she said. "Among our young workers, the problem is catastrophic."

Dixon said his new economic department would centralize various agencies now spread around the government and he suggested streamlining the city's business permits and building code process.

Dixon also proposed a new law to require supermarkets and large retail firms to give 90 days notice before they go out of business in order to give community groups and city officials time to avert such closings.

On tourism, Dixon said the city should put "greater emphasis on our unique black heritage with the creation of a Black Athletes Hall of Fame and funding for new black cultural attractions."

"People come to Washington to see the White House, white monuments and to read the words of historic white presidents," Dixon said in his prepared statement. "I want to show them a city illustrative of America's black heritage as well, black authors, black athletes, black inventors, black culture. That's America, too."

In a separate press conference yesterday, council member David A. Clarke (D-Ward 1), who is challenging Dixon for the chairman's job, said Dixon's criticisms of the Reagan administration "are subterfuges designed to conceal Dixon's own voting record" which Clarke contended "is the most Republican voting record of any member of the council."

Clarke said the Greater Washington Board of Trade, the area's most predominant business and trade group, has given Dixon a 92 percent approval rating compared to Clarke's 52 percent.

"Dixon would rather run against Reagan than me," Clarke said, "but the truth of the matter is that when it comes to the impoverished people of our city, his record is closer to Reagan's than any other member of the council."

At yesterday's Labor Day Mass, a crowd of about 1,200 persons, including political and union leaders from the metropolitan area, filled the Shrine of the Sacred Heart Catholic Church.

Seated on the front rows of the church were Mayor Marion Barry and his chief rival in the Democratic primary, lawyer Patricia Roberts Harris.

The two other Democratic candidates for mayor, council members Charlene Drew Jarvis (D-Ward 4) and John Ray (D-At Large), did not attend the 10 a.m. mass.

Dixon and Clarke also attended the mass, along with former council chairman Sterling Tucker, the third candidate running for council chairman, and council member Hilda Mason (Statehood-At Large), who is running unopposed.