Takeo Fukuda became prime minister a year ago this week with a confident proclamation that 1977 would be "the year of the economy." It was his way of summing up his mandate as the man who could pull Japan out of the three-year-old recession.

The words have returned to haunt him, because 1977 was largely a year of economic failures for Fukuda. Unemployment slowly rises in a country where that is not supposed to be troublesome. Businesses go bankrupt at a near-record pace. From Europe and the United States comes biting criticism about a large and growing trade surplus which Fukuda had proudly promised to eliminate.

Public opinion polls measure his declining support as touching a low at which former prime ministers have considered resigning. Big business, a pillar of Fukuda's Liberal Democratice Party, carps about his failure to stimulate the economy, and his predecessor, Takeo Miki, complaints publicly that Fukuda never does anything until it is too late.

Editorials decry a lack of leadership. A thorough Cabinet reshuffling jettisons the economic ministers who were supposed to chart a course for Fukuda's "year of the economy."

The economy's failure is especially bitter for Fukuda because his track record in economic matters had been so good and because he was widely reguarded as the man with the right answers. A cautious breaucrat and planner who came up through the Finance Ministry, he was the expert who knew when to tinker with discount rates, when to stimulate consumer demand, when to cool things off to avert inflation.He was pecularly the man for the '70s. It was said, because he advocated stable, slow growth after the high-growth bursts of the '60s.

The image of skillfull technocrat is gone now, replaced by that of the hapless optimist who never ealized how bad things were. Fukuda went to the economic summit meeting in London in May forecasting a 6.7 per cent growth rate and complete elimination of the trade surplus. Japan did not come close to either target. Now, largely to satisfy foreign insistence, he is projecting a 7 per cent growth rate next year while economists here and in Europe say will be lucky to hit 5 per cent.

Fukuda rejected a tax cut and pared down the pump-priming plans of his own bureaucracy in preparing his new budget this week. Why, an opposition leader asked recently, does the prime minister have to be pushed and shoved to do those things that his own talents and experience have taught him ought to be done?

Ironically, Fukuda enjoyed his biggest success in 1977 in a field thought to lie outside his natural abilities - foreign policy. His visit last summer to six nations of Southeast Asia is regarded as Japan's first major diplomatic initiative since World War II. Four years earlier, Prime Minister Kakuei Tanaka's visit to that region had provoked bitter anti-Japanese riots. Fukuda risked the lingering resentment from Southeast Asians' wariness of foreign instrusions since the United States pulled out.

In Manila, Fukuda proclaimed Japan's new doctrine of economic partnership. Coming from the leader of any other country, the words might have been written off as platitudes. For Japan, which is reluctant to venture into the distrustful world alone, it was a significant accomplishment.

But if the public opinion polls are accurate, the domestic approval that followed Fukuda's Southeast Asia visit has ebbed away under dissatisfaction with his handling of the economy. Only about a quarter of the people now approve of his administration, according to polls conducted by he Mainichi and Asahi newspapers, and the proportion registering actual disapproval has risen to nearly 40 per cent. The poolsters report that the overwhelming reason for rising disapproval is unhappiness with the economy.

There are many observers here who wonder how Fukuda came through the year with his government intact. He inherited a party ridden with factions last December and still under the ugly shadow of the Lockheed bribes scandal. It barely survived with a slim majority in the upper house after elections in July.

His party has only a five-vote majority in the lower house, sharply limiting his power to achieve such goals as the long-promised reform of the bureaucracy. One of his leading economic advisers told reporters recently that the government's thin support in the Parliament is perhaps the main reason Fukuda cannot make more compromises with the United States and Europe in trade matters.

Probably the best thing Fukuda has going for himself politically is his opposition. The Socialist Party is hopelessly divided and ineffectual. Three of its prominent members defected this fall to start their own party.