Japan's Liberal Democratic Party today won a solid electroal victory that will permit it to retain control of the government without resorting to a coalition with other parties.

Overcoming voter skepticism and the recent death of its leader, prime minister Masayoshi Ohira, the conservative pro-American party rolled up one of its biggest victories in years and can easily choose Ohira's successsor.

With most of the votes from Sunday's election tabulated, the Liberal Democrats had won 278 seats in the lower house of parliament.That was 20 more than it had before parliament was dissolved last month and 22 more than needed for a simple majority.

The overwhelming show of support for the ruling party demolished the plans of opposition leaders, who had hoped to move into a coalition government and share power for the first time in 25years.

The main opposition, the Japan Socialist Party, was holding its own.

But the Japan Communist Party suffered one of its biggest losses and the centrist Buddhist-oriented Komeito Laos was losing ground in lower house seats.

The big victory showed that the Liberal Democrat's had overcome the distrust of voters angry at a long chain of corruption scandals and dismayed by the party leadership's unceasing factional feuding.

They seemed to have accepted the Liberal Democrat's position that stability and prosperity of Japan would be better served by keeping the party in power rather than placing their trust in the opposition parties.

Almost all of the party's major leaders were elected. Former prime minister Kakuei Tanaka won reelection easily even though he is still on trial in the lockheed scandal case. He ran as an independent because he was forced to leave the Liberal Democratic Party when the scandal erupted, but he still runs one of the party's factions.

Both of the main candidates to succeed Ohira were recelted to the chamber.They are Toshio Komoto, the businessman-turned-political who enjoys wide support in the business community, and Yasuhiro Nakasone, the veteran politican who heads one of the party's five factions.

They are expected to fight it out for the premiership in what may be another bruising power struggle. Party leaders decided over the weekend to hold a special session of the new parliament in mid-July to select a new prime minister. Some members favor choosing only an interim caretaker to run the goverment until the party's regular election late this year.

A rainstorm in southern Japan was the only bad bit of election day weather. Good weather is usually viewed as a factor helping Liberal Democratic candidates because the party's voters are thought to be less disciplined and less motivated than those who support such opposition parties as the Socialists and Communists.

The election Sunday was an unprecedented doubleheader with control of both the upper and lower house at stake. One half of the 252 seats in the upper house were to be filled in the regular election for that chamber. All of the 511 seats in the more powerful lower house were being contested in a special election called when the Ohira government unexpectedly lost a no-confidence vote in parliament on May 16.

At the time parliament was dissolved, the Liberal Democrats had 258 seats in the lower house, two more than the necessary majority, and they could count on the votes of four conservative independents.

The party also held 124 seats in the upper house for a one-vote majority since six of the seats were vacant because of deaths or retirements.

It had been a noisy and at times intense campaign that for the most part became a kind of referendum on the Liberal Democratic Party itself. Opposition parties charged the Liberal Democrats have lost the trust of the people after 25 years in power because of repeated scandals and a history of severe factional feuds.

Even within the party there was a mood of defensiveness, with some of the more prominent candidates promising that the time has come for the party to clean house and abolish the factions that battled for power throughout the 1970s.

But for the most part, the party appealed to voters to keep it in power to maintain continuity, stability, and the extraordinary prosperity built up during the past quarter of a century. Its candidates depicted severe economic troubles if the opposition parties were allowed to have a share of power in future governments.

National defense also surfaced as an issue in a manner that showed politicians shifting perceptibly toward greater acceptance of a strong military. Defense is rarely a major issue in national elections. But this time the Liberal Democrats considered it important enough to claim that the opposition parties are too divided on defense to be permitted control of the government.

However, there was little discussion of how the government would pay for a bigger defense force. A tax increase was not seriously discussed.Last fall, Ohira's tentative proposal to raise taxes in order to lessen the country's dependence on national bonds proved to be highly unpopular and some blamed it for causing the ruling party's near defeat.

The party also had sought to turn Ohira's unexpected death into a campaign advantage, asking voters in effect to cast a sympathy vote for the party of the dead prime minister.

Since last fall, public opinion polls depicted declining support for both the Liberal Democratic Party as a whole and for the Ohira government in particular.

But last week, newspaper polls disclosed a nationwide trend of more support for the party. The newspapers translated that trend into a prospective safe but slim majority in the lower house for the Liberal Democrats. In the past, however, using poll projections to calculate gains and losses in parliament seats has proved unreliable.