Soviet Foreign Minister Andrei Gromyko arrived here today and held talks with Polish Communist Party leader Stanislaw Kania as the Polish national assembly took a first step toward implementing long-delayed economic reforms by streamlining the government bureaucracy.

It was the first meeting between Kania and a Soviet leader since Kania survived an attempt last month to oust him from office by hard-liners encouraged by a toughly worded Kremlin letter criticizing his leadership. The Polish Communist Party is preparing for a special party congress scheduled to open on July 14.

Polish officials said they welcomed Gromyko's visit as an opportunity to reassure the Kremlin that, despite the leadership changes and other reforms that are likely to result from the congress, the Communist Party will remain firmly in power. Kania has emerged much strengthened politically as a result of the Soviet letter, and it now seems virtually certain that he will be reelected party first secretary at the congress.

The proposals adopted today by the assembly, or Sejm, will result in an eventual halving of Poland's bloated economic bureaucracy. In a move that could also result in large redundancies among government officials, 10 of poland's 40 or so Cabinet ministries have been merged into five.

The new "superministries" are conglomerate departments, one of them, for instance, covering agriculture, food, and forestry, another mining and power. The changes, part of a general attempt to decentralize decision-making in the economy, were proposed by Premier Wojciech Jaruzelski in a speech two weeks ago.

In an accompanying government shuffle, eight ministers lost their jobs, including the higher education minister, Janusz Gorski, who was much criticized by striking students earlier this year. His highhanded manner and -- so some students claimed -- his ungrammatical Polish made him the butt of many university jokes.

The new ministers include Army Gen. Czeslaw Piotrowski, who has been made responsible for coal mining and power. He is the third serving officer in the government in addition to Gen. Jaruzelski and the interior minister, Gen. Miroslaw Milewski.

The new economic reforms are unlikely to encounter major opposition from Moscow as long as they help put the Polish economy back on its feet. The Kremlin's main concern is political: the preservation of Communist Party rule in Poland and the retention in the leadership of politicians upon whom it believes it can rely.

On these points, Kania is now in a position to provide some measure of reasurance for Gromyko. The official Polish argument in that the democratic election process has contributed to rebuilding the party's shattered morale. What is more, Kania's new prestige has enabled him to secure the election of several hard-liners in the Politiburo as delegates to the congress.

Official sources said Gromyko will return to Moscow Sunday. In addition to this meeting with Kania, has schedule includes two sessions with the ruling Politburo on Saturday as well as talks with the Foreign Ministry.

Since upheavals began here a year ago, there have been several meetings between Soviet and Polish leaders. Kania has been to Moscow twice. Kremlin emmissaries here have included the head of the Warsaw Pact military alliance, Marshal Viktor Kulikov, and the chief Soviet ideologist, Mikhail Suslov.

As a professional diplomat, Gromyko enjoys a much more benign image here than either Kulikov or Suslov and his visit therefore is being taken as a relatively positive sign. It is assumed that, despite its obvious concern, Moscow is prepared to allow the Polish congress to go ahead as planned and will await the result before deciding what to do next.