Spain, like two other NATO members, Norway and Denmark, would not allow nuclear weapons to be used from or stored in its territory, he said. No Formal U.S. Comment

There was no formal comment during today's action, but last week, during a briefing on President Reagan's European trip that begins Wednesday, a State Department official said Spain's membership would ''materially, morally and strategically strengthen'' NATO.

The reasons for Spain's late entry into NATO involved its severe domestic problems, including Basque separatism and a powerful military group opposed to an alliance that could make Spain a target of reprisals. Some NATO members resisted Spain's integration on the ground that Spain was neither economically nor politically in tune with the major Western powers. After the death of Francisco Franco there was an increasing feeling both on the part of the new democratic regime and of the Western powers that the best interests of both Spain and Western Europe lay in bringing Spain into the European mainstream. King Reviews Troops

In Spain today, that country's formal entry into the defense alliance coincided with ceremonies ending a traditional week of homage to the Spanish armed forces.

In Saragossa, site of Spain's top military academy, King Juan Carlos presided over a parade by nearly 10,000 Spanish troops, including armored and heavy artillery units and members of that country's elite foreign legion.

Spain's membership in NATO was particularly welcomed at this time after Greece's refusal to share in a joint NATO command that would cover defense of Greece and Turkey.

Greece left NATO's military command in 1974 after Turkey, also a member, invaded Cyprus. The Greeks returned in late 1980 but have since complained that they still did not have sufficient NATO guarantees against potential Turkish attacks. Invited to Join in 1981