Portugal was plunged into political uncertainty yesterday when Socialist Premier Mario Soares was dismissed by the president after a conservative party pulled out of the governing coalition.

Soares, whose leadership has given Portugal a measure of stability in the turbulent years since the leftist revolution of 1974, disclosed his dismissal following a brief meeting with President Antonio Ramalho Eanes Soares said he did not expect to be asked to form a new government.

This second political crisis Soares has faced in seven months under-scores the fragility of Portugal's young democracy.

The immediate cause of the quarrel between the Socialist and their conservative partners was the latter's demands for the resignation of Agriculture Minister Luis Saias. The conservatives charged that Saias was moving too slowly in restoring lands seized by squatters four years ago during a leftist-led campaign in rural areas they also said he favored Communist proposals in his policies.

The conservatives were also angered by Socialist plans for a free national health service and by delays in paying promised compensation for firms nationalized after the ouster of the rightist dictatorship that had ruled Portugal for over 40 years.

The three ministers from the Social Democratic Center Party resigned from the Cabinet over the weekend.

Eanes had reportedly been astonished when Soares did not submit his resignation immediately on Tuesday when the Social Democratic Center Party announced it was drawingits parliamentary support from the Socialists.

The Socialists hold 102 seats in the 263-member Parliament and the Democratic Center Party 41.

Before Eanes saw Soares he met for 11 hours with the 18-member Military Council of the Revolution which under the constitution serves as a political advisory body to the president. Diario de Lisboa, a newspaper that often reflects the thinking of the Council's left wing said a majority favored keeping Soares in the office.

President Eanes is expected to consult with the leader of Portugal's various parties before asking any of them to form a new government. Under the construction Eanes must take into account the number of votes each party won in the 1976 national elections.

There was a press speculation that Eanes may want a Cabinet of technocrats for the time being.

No new elections are neccessary until 1930 although Eanes could call a special election. Government spokesmen have said it would take five to six months to prepare for a special election, adding, however, that the process could be speeded up by parliamentary action