Organized labor is preparing for a United States without Ronald Reagan.

Convinced that union members are ready to return to the Democratic Party, labor unions are pushing a domestic legislative agenda in Congress that they hope will serve as the political glue for a broad new coalition of American workers -- union and nonunion, blue-collar and professional.

"We want labor to be seen as an institution that represents organized workers but also recognizes the needs of all workers," a top official of the AFL-CIO said.

For most of the decade, unions have been battered by a hostile White House and a changing economy that dramatically eroded labor's strong manufacturing base. Union leaders are convinced that their loss of members has ended and that their fortunes may be about to change.

As a result, organized labor has made Congress the main target of its efforts to regain political respectability and organize new members. The goal of labor's legislative agenda is to capture the economic middle ground for most working Americans.

"There are some very significant problems in the work force in the 1980s, and no one on the national level is addressing them," an AFL-CIO official said.

At the core of labor's legislative agenda are modern workplace issues that reflect demographic changes in trade-union membership and the workplace as a whole as increasing numbers of women, minorities and immigrants enter the job market. The issues include child care, parental leave, minimum wage and mandated health benefits.

With the exception of child care -- an issue beginning to confront organized labor as more women join unions -- the basic items on labor's legislative agenda have little direct or immediate impact on most union members.

One of the best examples of this is the parental leave bill. The legislation, opposed by the Reagan administration, would allow parents as many as 15 weeks of unpaid leave when a baby is born. "Up here, that's viewed as a yuppie ladies' bill," a key congressional aide said. "What low-paid woman can afford to take off 15 weeks without pay?"

Mandated health-insurance benefits is another area of minimal concern to most union members, who receive medical coverage through their contracts. Last year, labor essentially opposed a health insurance proposal sponsored by Sen. Edward M. Kennedy (D-Mass.), arguing that it interfered with collective bargaining. This year, labor is supporting the Kennedy bill, although congressional sources claim that "they're not working it hard."

It is issues such as parental leave and mandated health insurance that union leaders are counting on to build a new political coalition and to help eradicate the special-interest label that haunted them throughout Walter F. Mondale's unsuccessful presidential campaign in 1984.

"These bills will help bring us back into the mainstream," an AFL-CIO official said recently. He said it is particularly important that labor not be seen as just another special interest or single-issue group.

Labor believes that it will be helped in this effort by the Reagan administration, which basically opposes the legislative package. Ironically, the White House opposition is much the same as labor's past position on the health bill. Issues such as child care and parental leave, administration officials say, should be worked out between labor and management and not mandated by the government.

If all goes according to labor's plan, Ann Dore McLaughlin, President Reagan's nominee as secretary of labor and potentially the only woman in the Cabinet, will spend much of her year in office opposing issues that unions believe will have great appeal to women voters.

McLaughlin is known to view the child-care and parental-leave proposals as unnecessary government intervention, and the administration has opposed the federal minimum-wage bill and the Kennedy health proposal.

It is unclear whether any of the legislation being pushed by labor, with the possible exception of the minimum wage, will be approved by Congress before the 1988 elections. But congressional sources said they are not sure that labor really cares. "They want to make these the issues in the campaign," a key congressional aide said.

Labor is working hard to avoid the political union label in pursuing its coalition strategy on broad workplace issues.

Union officials point to the coalition that opposed Supreme Court nominee Robert H. Bork as an example of how unions need to proceed in the year ahead. When they set out to oppose Bork, AFL-CIO strategists were careful to oppose his nomination on broad legal issues, not his views on labor. They said they did not want to risk being branded with the single-issue label as are gay-rights or pro-abortion groups.

AFL-CIO President Lane Kirkland outlined labor's strategy at the federation's Miami Beach convention last month. "As we enter the twilight months of the Reagan era, it is long past time for a new national course," he said in his opening address.

"As we go into another presidential election year, we shall be exposed, I expect, to the mindless abuse of the term 'special interest,' " he said.

Kirkland went on to outline labor's legislative agenda with the warning that "it's about time our politicians acknowledged the difference between representative institutions rooted in our democratic system and working to lift up the less powerful, and the narrow, carnivorous interests nurtured in the trough of Ronald Reagan's social philosophy."

Accompanying labor's legislative effort in the next year will be a $13 million public-relations campaign approved by the AFL-CIO last month. The campaign is designed to improve labor's public image, particularly among younger workers.

It will be waged primarily on radio and television over the next two years and, as the AFL-CIO executive council said, attempt to "raise the level of public understanding of unions and of the AFL-CIO and to increase the predisposition of a new generation of American workers (20 to 40 years old) to union organization and those workers' understanding of how unionism responds to their own needs and concerns."

Labor's longer-term legislative agenda is tailored much more closely to unions' specific needs. A key union lobbyist said the next items involve pension protections and development of an industrial policy. "There's a degree of imbalance {in labor-management relations} that cries out for an industrial policy," he said.

Part of that industrial policy is apt to be a proposal to rewrite the nation's basic labor laws to reflect changes in the economy and workplace.

Kirkland, in a Labor Day interview, said the AFL-CIO is drafting labor law revision proposals against the time when unions have "some prospect of having a receptive ear in Congress."

He said he could see that day. "I think there will come an opportunity within our life spans, and I want to be ready when it does come," he said.