Democratic candidates are getting more money from special-interest groups than Republicans and corporations are splitting their contributions between the parties, a government report said yesterday.

The Federal Election Commission, which monitors campaign spending said Democratic candidates have received 63 percent of the money spent by political action committees in the last two years and Republicans 37 percent.

In dollars Democrats got $11.8 million and Republicans $7 million. Not surprisingly, the Democrats received their biggest single support from unions - 94 percent of labor's political funds went to Democraticcandidates.

While some liberals had expected corporations to focus on Republicans and, conversely. GOP National Chairman William Brock had said they would concentrate on Democrats, big business has instead spent 47 percent of its campaign dollars on Democrats and 53 percent on Republicans, the FEC said.

But Republicans have gotten 71 percent of the political funds from the so-called non-connected organizations, which include such conservative groups as Citizens for the Republic, the National Conservative Political Action Committee and the Committee for the Survival of a Free Congress.

Those three groups have collected nearly $7 million, the FEC said.

Corporate political action committees (PACs) have been proliferating like bunnies - four years ago there were 89 and now there are 776 - and the FEC reports shows they have supported incumbents overwhelmingly, regardless of political stripe.

For example, in House races corporate PACs spent $1.4 million on Democratic incumbents and only $285.012 on Republican challengers. They spent $1 million on Republican incumbentsand only $85,873 on Democratic challengers.

In Senate races corporate PACs spent twice as much on Democratic incumbents as on Republican challengers - $334.768 to $165.351 - and seven times as much on Republican incumbents as on Democratic challengers - $691.709 to $94.423.

Fred Wertheimer, senior vice president of Common Cause, the nonpartisan lobbying organization that advocates public funding of congressional campaigns, said the figures "confirm once again that corporate PACs view campaign as investments.

"They are investing in incumbency - in who holds power, who has the committee assignments," he said. "They do not view their contributions as risk capital."

Wertheimer also said special-interest groups generally will probably spend $30 million on the current campaign. According to Common Cause figures, congressional candidates raised $8.5 million from special-interest groups in 1972, $12.6 million in 1974 and $22.5 million in 1976.

The FEC report said that as of Sept.30, political action committees had $19.2 million in hand.

The report showed that PACs affiliated with trade, membership or health associations doled out the largest single amount - $6.2 million. Labor organizations gave $6 million, and corporate PACs, $4.7 million.

The trade-membership-health groups gave $3.1 million each to Democrats and Republicans; corporations gave $2.5 million to Republicans and $2.2 million to Democrats, and labor organizations gave $5.6 million to Democrats and $400,000 to Republicans.

Groups affiliated with the American Medical Association gave more than $1 million to candidates. The second largest spenders were PACs affiliated with the National Association of Realtors, which contributed $572,508. The AFL-CIO's COPE Political Contributions Committee came in third with $536,760.

Five of the top 10 spenders were union political funds. Besides the AFL-CIO, they were affiliates of the United Auto Workers, United Transportation Union, Steel Workers of America and the Seafarers International Union.

Others in the top were affiliates of the National Automobile Dealers Association, American Dental Association and the Associated Milk Producers Inc.

The largest single fund-raiser was Ronald Reagan's Citizens for the Republic, which has collected nearly $2.7 million. The largest labor fund-raiser was the AFL-CIO with $1.4 million. The AMA has raised nearly $1.6 million; the National Association of Realtors, $1.5 million; the Gun Owners of America, $1.3 million, and the auto dealers, $1.24 million.

Wertheimer said the Texas senatorial campaign between Republican incumbent John G. Tower and the Democratic challenger, Rep. Bob Kreuger, shows how corporate contributors are hedging their bets.

Wertheimer cited a Common Cause study that shows Braniff Airlines has given $3,000 to each candidate; Bracewell & Patterson. a Texas law firm specializing in energy, $1,000 each; First International Bancshares, $1,000 to each, and Houston Oil and Mineral Corp., $1,000 to each.

Other companies weighted their contributions, he said. For instance, Coca Cola gave Tower $500 and Krueger $1,000; General Electric gave Tower $500 and Krueger $300; General Motors spent $1,500 on Tower and $1,000 on Krueger, and U.S. Steel gave Tower $1,000 and Krueger $500.

"It's like taking both sides in a football game." Wertheimer said. "You're bound to have a winner."