Spanish Premier Adolfo Suarez appointed a moderate Cabinet tonight to deal with the country's grave economic crisis and heated demands for regional self-rule. He also sharply reduced military influence in Spain's administration for the first time since the 1936-39 civil war.

Before announcing Spain's first elected government in 41 years, the premier reorganized the administration under a decree signed by King Juan Carlos. The royal decree eliminated the army, navy and air force ministries, which weilded unusual political power throughout the 37-yeart dictatorship of Generalissimo Francisco Franco.

From now on the armed services - which tried to halt the King's transition to democracy - will be represented by the newly created Minister of Defense. Suarez named Lt. Gen. Manuel Cutierrez Mellado, who served as his chief military minister for several months, to take over the defense post with the rank of first vice premier.

The 18 civilian ministers included new faces from the Center Democratic Union, the 12-party coalition that helped Suarex win the June 15 parliamentary elections and fiuve holovers from the previous government. The Democratic Union, which Suarez has tried to forge into a major centrist party with what he has called a "left-leaning social democratic ideology," won 163 seats in the Chamber of the Deputies and 105 Senate seats. There are 350 elected deputies and 207 senators, 41 appointed by the King.

The five ministers retained by Suarez - including Foreign Minister Marcelino Oreja, a Christian Democrat, and Interior Minister Rodolfo Martin Villa, a former Francoist - are senators by royal appointment.

Pio Cabanillas, fired by Franco in 1974 as information minister for giving the press practically full freedom, assumed the new Cultural and Welfare Ministry, which will oversee the media, book publishing, films and the theater. He is the only minister who served in a Franco cabinet although others, including Suarez, held high office under Franco.

Suarez created an economic super ministry, to be headed by economist Enrique Fuentes Quintana, a technocrat, to deal with mounting inflation, now running at a 30 per cent yearly rate, an unemployment.

The new finance minister, Francisco Fernandez Ordonez, a Social Democrat, has advocated a structural reforms into the economy to stimulate investment and his program is apparently acceptable to the Socialist Workers Party, which came in a surprising second in last month's election. The party had stated that it will be in opposition and had demanded that the new Parliament make the economy and a new constitution the first order of business.

Among the most significant new Cabinet appointments was that of Manvel Clavero as minister for relations with the regions. He advocates a degree for autonomy for all of Spain's regions his native Andalusia, Catalona, the Basque country, the Canary Islands and poverty-stricken Extremandura.

Over the weekend Clavero and other members of Suarez's party proposed self-rule as a goal for Center Democrats and for the country. The premier said at a recent press conference that a new regional law will be written by the Parliament.