The battle for a new chairman of the Democratic National Committee formally opened on this Virgin Island today, as six candidates paraded before state party chairmen from around the country with a warning that the Democrats must change their image if they hope to recapture the White House in 1988.

At the same time, the state chairmen moved to rein in a new party commission created last summer after complaints by candidates Jesse L. Jackson and Sen. Gary Hart (D-Colo.) that the 1984 nominating rules were unfair to them and tilted to help Walter F. Mondale, who won the nomination but lost the race to President Reagan in a landslide on Nov. 6.

The Association of State Democratic Chairs (ASDC) unanimously approved a resolution urging the Democratic National Committee (DNC) to let the party's four regional caucuses choose 40 of the 50 members of the new Fairness Commission, an effort to prevent 1988 presidential aspirants from dominating the group.

Members of the association also urged the DNC to order the Fairness Commission not to reduce the number of unpledged, elected officials who are to obtain automatic seats at the national convention. Hart had sharply criticized the role of these "superdelegates."

The speeches today from the six announced aspirants for national chairman marked the first step in a process that will culminate early next year when the DNC meets to choose a successor to Charles T. Manatt, whose term is expiring.

Many Democrats see the choice of a new chairman as the first step in rebuilding the party in the wake of Reagan's 49-state victory over Mondale, and the contenders today stressed the obstacles involved in regaining the majority status the party enjoyed since the New Deal days of Franklin D. Roosevelt.

"The election of a new chairman must be a symbol that we are going back after middle America," said ex-representative John J. Cavanaugh (D-Neb.).

Paul G. Kirk Jr., party treasurer and a former adviser to Sen. Edward M. Kennedy (D-Mass.), said Democrats have to "say no to excessive demands placed on the party" by various constituency groups and should not be captive "of any candidate or region of the country."

Kirk evoked a strong response when he condemned Reagan for invoking the names of Democratic presidents in his reelection bid, saying Reagan "stole our political heroes."

But he warned that before the Democrats pick a chairman they must agree on where they want to take themselves and the country.

Others who spoke today were Sharon Pratt Dixon, a national committee member from the District of Columbia; Duane B. Garrett, who was national cochairman of Mondale's presidential campaign; Robert J. Keefe, a veteran Democratic consultant and former DNC director, and Nancy Pelosi, former California Democratic chairman. Party officials expect other candidates to emerge in the next month.

Democratic governors, led by Bruce Babbitt of Arizona and Charles S. Robb of Virginia, are promoting the idea of an elected official or retiring elected official as the new chairman. Among the candidates they have contacted who are interested are retiring Gov. Scott Matheson of Utah and retiring Sen. Paul E. Tsongas (D-Mass.). Another name on the list is former North Carolina governor Terry Sanford.

Rep. Michael D. Barnes (D-Md.) also had a representative on the scene here to let state chairmen know that he might be interested.

Some Democrats have talked about a two-tier leadership, with a general chairman as spokesman and a chairman as day-to-day manager. Rep. Tony Coelho (D-Calif.) favors a change in the party charter to permit that, but many state chairmen here expressed skepticism.

The Fairness Commission resolution was a clear sign that the party leaders hope to avoid a lengthy fight over new rules for 1988, that they want more control over what happens, and that they disagree with at least some of the complaints about the rules.