Spanish Premier Adolfo Suarez's ruling Center Democratic Union appeared today to have won enough parliamentary seats to continue to rule Spain at least as a strong minority government.

Regional automist and separatist parties all over the country also did better than expected, however, especially in the separatist-inclined Basque country. This raised the prospect of confrontation.

With nearly half of the vote counted nationally, the ruling Center Democrats had 35 percent of the vote ocmpared to 29 percent for their main rivals, the Socialists. In kthelast elections, in 977, the Center Democrats won 34.7 percent and the Socialists 33.7 percent.

The Communists were winning 9 percent of the vote, the same as in 1977. That eledtion, the first free vote after Generalissimo Francisco Frnco's death, in 1975, was for a parliament to write a constitution. Yesterday's vote was the first unde that new democratic charter.

The probable turnout nationally was 67 percent, compared to 78.3 percent in 1977 in an electorate of 27 million.

The biggest losses nationally were suffered by the rightists led by Franco's former information minister, Manuel Fraga Iribarne. His Democratic Coalition appeared to have dropped from 8 percent in 1977 to 5 percent.

"Now we are going to have stable government in Spain," said Jose Perez Llorca, the ruling Center Democrats' parliamentary leader. "It's the best news for the West in a year." Then, in an interview at a party victory celebration, he added, "But I know, I know, the Basque country..."

A Center Democrat analyst said his party's projection from key districts showed regionalist parties winning about 30 seats in the 350-member lower house, the Congress of Deputies. He said he thought the three Basque nationalist parties would win a dozen seats, the Catalans about 10, plus a scattering of reginoalists from Andalusia, Aragon, Galicia and the Canary Islands.

The biggest single regionalist surprise was the showing of the local socialist party in Andalusia, Spain's poor southern area. Many analysts have predicted that it could turn into Spain's next major headache. The local socialists seemed to have won five or six seats at the expense of the national Socialists, who opposed Andalusian regionalism.

Subject to confirmation in the final results, the returns appeared to offer more option for forming a government than the once foreseen necessity of a coalition of the two main parties, the premier's Center Democrats and the Socialists.

Respected public opinion polls had suggested that outcome. Many commentators had expressed fear that such a result would represent a major setback to the trend toward a twoparty system in Spain.

The 1977 election gave 168 stats to the Center Democrats and 122 to the Socialists. The Communists had 19 and Fraga's rightists 17. The exact distribution of deputies this time will be known only much later inthe day, after the calculations under Spain's complex proportional representation formula.

The electoral law is designed to produce this proportionately high representation for the conservative rule administrative provinces that normally vote for Suarez.