Linda Chavez, a Republican candidate for U.S. Senate in Maryland, lashed out yesterday at Democratic critics of the Reagan administration's policies in Central America and reiterated her support of U.S. aid to rebels fighting the government in Nicaragua.

Chavez, a former White House aide of Spanish descent, issued her first position paper on Central America before a group of Hispanic Republicans at a Cuban-American restaurant in Takoma Park. The 45-member group, composed largely of Cuban immigrants, endorsed her for the Republican nomination in the Sept. 9 primary.

In appealing to a conservative segment of the growing Hispanic community in the Washington suburbs, Chavez criticized the Democratic Senate candidates who, she said, "by and large oppose the president's efforts" to fund the contras, or rebels, fighting the Sandinista government in Nicaragua. Chavez also distributed a "point paper" outlining what she believes are human rights violations and other alleged abuses of the Sandinista regime.

Two of the nine Democrats running in the race, Rep. Michael D. Barnes of Montgomery County and Gov. Harry Hughes, have been endorsed by other Hispanic groups in Montgomery County.

Chavez told the Hispanic Republican group that she is running to succeed retiring GOP Sen. Charles McC. Mathias Jr. in part because "I share your values and your hope for freedom, for people who are not in the room but who live behind a wall of totalitarian dictatorship."

Chavez's opponents in the primary are former Baltimore businessman Richard P. Sullivan, Silver Spring lawyer George W. Haley and six less known candidates.

Both Sullivan and Haley said yesterday that they also support Reagan's policies in Central America, particularly a $100 million aid package recently approved by Congress.

Barnes, chairman of a House Foreign Affairs subcommittee that deals with Central America, has been an outspoken critic of the administration's policies in the region, particularly Reagan's efforts to increase U.S. funds for the contras.

The third major Democratic candidate, Rep. Barbara A. Mikulski of Baltimore, opposes aid to the contras. Hughes has endorsed a part of the administration package that called for $30 million in humanitarian aid to be distributed through international charitable organizations "with strict accountability," according to a spokesman.

According to the 1980 census, Hispanics -- defined as persons who identified themselves as being of Spanish origin -- comprised only about 1.5 percent of Maryland's 4.2 million population. But a majority of these residents, 57 percent according to the census, are concentrated in Montgomery and Prince George's counties.

Hispanics comprise less than 2 percent of the voting age population. Because registration statistics are not kept by race, the number of Hispanics that are registered voters is not known.

Luis Queral, a native of Cuba who left in 1957, as Fidel Castro's revolutionary movement was gaining strength, said, "We support Chavez because of her views on Central America, her commitment to a strong America and her support of conservative principles." Nevertheless, Queral, a Baltimore County surgeon who organized the group supporting Chavez, said he and other supporters were particularly proud to work for a candidate who "shares our heritage."