David J. McDonald, 76, a former president of the United Steelworkers who led his union in three strikes and then helped form a group to avoid such confrontations, died Wednesday at Desert Hospital in Palm Springs, Calif.

He had been hospitalized July 27 for treatment of pneumonia. An autopsy was scheduled to determine the cause of death.

Mr. McDonald became acting president of the Steelworkers, the third largest union in the nation at the time, in November 1952. This was a week after the death of Philip Murray, the union's founder and first president and the president of the Congress of Industrial Organizations as well. As a close associate of Murray for 30 years, Mr. McDonald played a role in the turbulent struggles that brought the labor movement into the front ranks of national power.

In 1953, Mr. McDonald was elected to a full term as president of the Steelworkers. He held office until 1965, when he was defeated by I. W. Abel after a bitterly fought election campaign.

Mr. McDonald first led the Steelworkers on strike in 1955. The walkout lasted only a few hours. The second strike was in 1956 and lasted 34 days. The third was in 1959 and 1960 and extended over a period of 116 days.

Out of the last strike, which was said to have been ended with the help of such diverse persons as Richard M. Nixon, then the vice president, and Joseph P. Kennedy, the father of President John F. Kennedy, there developed the Human Relations Council. It was an industry-labor group and its purpose was to settle labor disputes without strikes. Mr. McDonald was credited with persuading labor to join it.

In 1963, Mr. McDonald and the steel companies negotiated a contract which drew high praise from President Kennedy. He called the agreement an act of "statesmanship" on both sides of the negotiating table. He said it would not cause inflation and at the same time would benefit the steel workers.

Mr. McDonald always was a supporter of democratic capitalism. He is said to have coined the phrase "mutual trusteeship" to describe what he regarded as a proper relationship between unions and management.

Gains won by the steelworkers under Mr. McDonald included higher wages, greater job security, improved retirement benefits, inducements for early retirement, and a 13-week vacation for every worker every five years. The extended vacation was the achievement that Mr. McDonald best liked to remember.

"That was my brainstorm," he said in an interview after his retirement. "I still get postcards from all over the world - Rome, Hawaii - saying, "Thanks, Dave, I'm enjoying this." I feel very proud of it."

Although he was born into a family with strong union ties - he used to say, "I was born with a union spoon in my mouth" - Mr. McDonald looked more like the president of a corporation than the leader of a trade union. His hair was silver and gray and he smoked a pipe. His suits were expensively cut, he enjoyed staying in famous hotels and dining in famous restaurants, and he was welcome in the Duquesne Club, the Pittsburgh stronghold of the steel barons.It was said that there was more about him of silk than of steel.

These remarks became jibes used against Mr. McDonald when I. W. Abel, the USW's secretary-treasurer, took him on for the presidency. Abel, who headed the union until his retirement in 1976, said that Mr. McDonald represented "tuxedo unionism."

But Mr. McDonald was of the generation of union leaders who brought labor to prominence. Others were Walter Reuther, of the United Auto Workers; John L. Lewis, of the United Mine Workers, and George Meany, now the president of the AFL-CIO, and, of course, Philip Murray, whose CIO later joined the American Federation of Labor to form the AFL-CIO.

A statement issued yesterday on behalf of Lloyd McBride, Abel's successor as head of the steelworkers, and other high officials of the union said:

"Dave McDonald was controversial and colorful to those outside the Steelworkers, but his achievements and accomplishments in the collective bargaining area were those that will be recalled by many of our members."

David John McDonald was born in Pittsburgh on Nov. 22, 1902. His father was a steelworker and a union man and it is said he was out on strike the day his son was born. The young McDonald went to high school for two years and then went into the steel mills, where he earned 22 cents an hour. He also studied accounting at Duquesne University and became a typist and switchboard operator for the Jones & Laughlin Steel Co. at $80 a month.

In 1923, a friend told Mr. McDonald that Philip Murray was looking for a secretary.Mr. McDonald applied for the job and got it.

At the time Mr. McDonald went to work for him, Murray was vice president of the United Mine Workers. When John L. Lewis asked Murray to form the CIO, Mr. McDonald became secretary-treasurer of the Steelworkers Organizing Committee, which was set up in 1936. He was active in organizing, running the union, and negotiating. The United Steelworkers was formed in 1942 and Mr. McDonald continued to serve as secretary-treasurer.

Mr. McDonald's marriage to the former Emily Lou Price, a member of a prominent Cleveland family and a former secretary of John L. Lewis, ended in divorce.

Survivors include his wife, the former Rosemary McHugh, and a son by his first marriage, David Jr. CAPTION: Picture, DAVID J. McDONALD