President Francois Mitterrand tonight put together a drastically smaller Socialist-led government to steer France through a period of economic austerity following the third devaluation of its currency in less than 18 months.

The prime minister, Pierre Mauroy, remained head of the new government, which contained 14 senior ministers as opposed to 43 in the previous administration. Communist representation in the Cabinet was reduced from four ministers to two, reflecting the party's continued decline in electoral popularity.

The announcement of the government shake-up, just before midnight, ended uncertainty and speculation following a setback early this month for the left in municipal elections and a crisis last weekend over currency realignments within the European Community. The 66-year-old president is due to make a nationwide television broadcast Wednesday to explain how he plans to cut France's trade deficit and 9 percent annual inflation rate.

Key figures in the new government included Jacques Delors, who negotiated the currency realignment in Brussels, who acquired the budget portfolio in addition to that of minister of finance and economy. A former top aide to Mitterrand, Pierre Beregevoy, was named to another newly created "super-ministry" to coordinate social affairs.

The major casualty in the reshuffle is Jean-Pierre Chevenement, the controversial minister of industry who heads a left-wing splinter group within the Socialist Party.

The choice of Mauroy to head the new government represents an attempt by Mitterrand to reassure his left-wing supporters that their interests will continue to be looked after despite what political analysts said was a slight shift toward the center in the composition of the new Cabinet. As prime minister since May 1981, when he became head of the first left-wing government in 24 years, Mauroy is one of the few politicians acceptable to both the Communists and all segments of Mitterrand's own Socialist Party.

The genial 54-year-old prime minister has cultivated an image of an economic realist who is at the same time a "man of the left" with a strong attachment to his working-class origins. Together with Delors, he was believed to have resisted pressures from left-wing Socialists to take France out of the European Monetary System during the recent currency realignment crisis.

Such a step undoubtedly would have led to disruption of French ties to Europe and the establishment of protectionist trade barriers. Its advocates said that it would have helped promote economic growth and cut unemployment.

Senior officials here have attributed Mitterrand's delay in announcing the reshuffle, which originally had been expected to take place last week, to a game of economic brinkmanship with West Germany. By keeping his European partners in suspense about the makeup of the new government, Mitterrand was in effect threatening them with the possibility of a major change of political and economic direction in France unless they helped bail the country out of its economic plight, according to these officials.

The ploy seems to have worked in part, since the West Germans were obliged to bear the brunt of the currency realignment by revaluing the mark upward by 5 percent while France devalued the franc only 2.5 percent

The disagreements at the meeting, however, have soured relations with West Germany at the start of Chancellor Helmut Kohl's tenure of office.

Among the Communist ministers to lose their posts in the Cabinet is Anicet le Pors, the minister for public administration. But it is possible that he will be named a junior minister. The Communist Party's executive Politburo held a meeting tonight to discuss the appointments before giving its agreement.

Replacing Chevenement is Laurent Fabius, a close associate of Mitterrand. Michel Rocard, who is seen as a possible rival to Mitterrand, has been transferred from planning to agriculture--a sensitive post that will associate him more closely with the day-to-day running of the government.

The former minister of agriculture, Edith Cresson, was appointed minister of foreign trade. The ministers of foreign affairs, interior, transport and justice will stay on.