BRUSSELS, April 4— The civilian Government temporarily suspended King Baudouin I from power today after he declared that he could not, in good conscience as a Roman Catholic, sign a new law permitting abortion.
After declaring the King ''unable to govern,'' the Cabinet assumed the King's powers and promulgated the abortion law, which was published in the official gazette. And it called the Chamber of Deputies and the Senate back from Easter vacation for a special session on Thursday.
The lawmakers will be asked to vote on the proposition that the 59-year-old King is once again able to govern. Approval is expected.
Seen as Acceptable Way Out
There was uproar in some political groups that have traditionally been opposed to the monarchy. But television and press comment tonight generally supported the apparent solution to the King's problem as an acceptable outcome.
Belgium has 25 political parties divided among speakers of French and Flemish and four self-governing regions. Solutions that give each participant a taste of victory in complicated circumstances are called '' a la Belge'' - in the Belgian manner.
Belgium, a country of 10 million people, sometimes puts itself forward at international gatherings as a good model to follow when big powers and unyielding ideologies cannot find common ground.
Today's events were the first time since the creation of Belgium and its constitutional monarchy in 1830 that the special powers of the Government had been used in such a way.
Not the Intended Use
According to scholars, the clause of the Constitution cited was drafted to cover eventualities in which the monarch was incapacitated by illness or insanity. Some political leaders today attacked the use of the clause to cover dissent, but none said they would vote against Baudouin's return to power.
The only other time the Government had taken over the King's powers was in 1940, when Baudouin's father, Leopold III, remained behind with the army in Belgium after the Nazi occupation while the Cabinet fled to London. Leopold, suspected of collaboration with the occupiers, was never permitted to return to the throne and gave way to his 20-year-old son in 1950 after a tumultuous referendum.
Over the centuries, Belgian territory had been overrun or occupied at one time or another by most European powers. In 1830 the Belgians revolted against the Dutch, who then occupied the country, and set out to find a King who could assure them neutrality among the surrounding big powers -France, England and Prussia. They settled on Leopold I, Baudouin's great-great-grandfather, and depended on his status as an uncle of England's Queen Victoria to keep them safe.
In Belgium, the King must sign legislation before it can become official, but he has few other political powers. Until today, no king in Belgium in this century had refused to sign a law passed by Parliament.
'State of Distress'
The abortion law, which permits an interruption of pregnancy within 12 weeks if the woman and her doctor decide that she is in a ''state of distress,'' replaced a ban on abortion that had been in effect since 1867.
In the last 17 years, there had been at least 15 laws permitting abortion proposed and defeated. Until the vote last week, Belgium and Ireland had been the only countries in Europe banning abortion. About 90 percent of the population of Belgium is Catholic.
The King had often indicated in speeches his concern as a Catholic for human life, but his attempted veto of the legislation was unexpected.
He and his wife, Fabiola, a Spanish princess, have not been able to have children, so under Belgium's law of exclusively male succession, his brother's son is the Crown Prince. But Belgium has a custom that the seventh son or seventh daughter in one family have the king or queen as godparent, and Baudouin and Fabiola enter into these duties enthusiastically.
