The NAACP opened its 74th annual convention here trying in vain to soothe the wounds of a bitter feud between its board chairman and executive director and to focus instead on economic and political action, much of it directed against President Reagan.

Convention organizers had hoped that the five-day gathering of nearly 4,000 delegates would focus on building membership in the nation's oldest civil-rights organization and flexing political muscle for the expected appearance of several Democratic presidential hopefuls.

But those hopes faded this morning when the NAACP board, for the third time in six weeks, voted its lack of confidence in Chairman Margaret Bush Wilson by adopting a special report that found no cause for her abrupt eight-day suspension of executive director Benjamin L. Hooks in May.

Wilson, a tough-willed lawyer who came to the convention with a prepared keynote address even though she had been banned as keynote speaker, called the report biased.

"It's not a complete resolution of the issues. It's his side," she said.

Told of her remarks, board Vice Chairman Kelly M. Alexander Sr. said he sees no signs of unfairness nor any likelihood that Wilson will address the convention.

It was not clear whether Wilson would make any effort to dramatize her concerns to delegates. Earlier today, she sat unobtrusively on the podium for several preliminary addresses, and no one acknowledged her presence.

The feud between Wilson, board chairman since 1975, and Hooks, executive director since 1977, became public May 18 when, without consulting other board members, she suspended him for alleged improper conduct and lack of cooperation.

Other board members and local organization leaders denounced the suspension, and Wilson reinstated Hooks, saying an initial reason for the suspension--her fear that he would not cooperate with an ongoing audit--had been resolved because the audit was complete.

On May 28, in special session without Wilson, the board rejected the suspension as unnecessary and sought her resignation. She refused.

Two weeks later, she read the board a 33-page report detailing contentions of mismanagement by Hooks. The board rejected it, stripped her of all but honorary powers and again asked her to resign. Again she refused.

The special report adopted today gives the first point-by-point responses to Wilson's allegations, saying actions by Hooks that she had characterized as intemperate "did not occur" and that Hooks had not tried to impede the routine audit.

Its only point of agreement with Wilson is that the NAACP has a deficit. But, it asserted, "This deficit did not creep up on us but is one we have been aware of through the years, and much of the deficit is the result of poor judgment on the part of the chairman . . . ."

Board Vice Chairman Alexander told the convention tonight, "Black Americans are being challenged today as never before in the nation's history. We are on the eve of the 21st century, and black Americans still have a shopping list of unfulfilled promises of democracy."

Alexander pinned much of the blame on the Reagan administration and urged blacks to vote in next year's presidential and congressional elections and express their concerns about domestic and foreign policy.