Yugoslav President Tito's state visit to Washington this week will climax what has been - even by his standards - a remarkable year.

For the past seven months, the 85-year-old Yugoslav leader has been making a Grand Tour - quite possibly a farewell tour - of world capitals.

Feted at the Kremin, wined in the Elysee Palace and dined in Peking's Great Hall of the People, Tito on Tuesday will become the first Communist leader to visit President Carter's White House.

Tito will conclude the week, more over, by flying to London to be entertained by Queen Elizabeth at Buckingham Palace.

For a man born the son of a peasant in an obscure province of the now defunct Austro-Hungarian empire, it is quite an achievement. Having spent the greater part of his life hunted down by his opponents, first by the royal Yugoslav police when he was a young Communist organizer and later as a wartime-partisan leader by 20 German divisions, Marshal Tito is now enjoying being wooed by virtually all sides of global opinion.

Dragan Bernardic, special assistant to the foreign minister for American affairs, points out that Yugoslavia is one of the very few countries which has good relations with all three major powers. "Some countries have good relations with two of them, but very rarely with all three at once. What is more, we are also on friendly terms with all the socialists except Albania - that means the Soviet bloc, the Eurocommunists, the Chinese, the Vietnamese, the North Koreans, and so on. It has not been easy to reach this position, in fact a lot of effort has gone into it," he says.

One by-product of this highly sucessful foreign policy is a collection of now embarassing denunciations of Tito from countries which have since come to change their veiws about him. There is, for example, Stalin's boast: "I have only to lift my little finger and there will be no Tito." Or the description of Tito by the Peking People's Daily as "A dwarf kneeling in the mud and trying with all its might to spit a giant standing on a high mountain.

Today Stalin's political heirs have formally recognized Yugoslavia's right to independence (although they may have some reservations in private) while the once-doctrinaire Chinese Communists are themselves toying with Tito's heretical doctrine of workers self-management.

There are no such obvious skeletons in the cupboard of U.S.-Yugoslav relations, but there have been some periods of strain. The most recent was during the Ford administration when the U. S. ambassador in Belgrade, Laurence Silberman, advocated a policy towards Yugoslavia based on a narrower definition of American interests.

Yugoslav officials have welcomed the improvement in relations under President Carter. A senior Yugoslav diplomat commented recently that Washington now views Yugoslavia as a factor, rather than a mere object, in international relations and is respectful of Tito's position as a leader of the nonaligned movement.

Evidence of the change is a series of 10 messages exchanged between the two presidents over the last 10 months. Described as "unprecedented" by Yugoslav officials, they have ranged from request for Tito's good offices with countries like Ethiopia and North Korea to a sharing of views on the Belgrade conference.

In part, Tito's achievement in securing good relations with everyone is due to the simple fact that he has managed to outlive his formidable array of opponents on both left and right - from Hilter to France, from Stalin to Mao Tse-tung. But it is also a testament to one of the great most effective political leaders of the 20th century.

It is Tito as a brilliant politician, rather than as a military strategist or ideological thinker, that has most impressed his friends and enemies alike. Milovan Djilas, once his aide but now his critic, has remarked on Tito's extraordinary capacity for sensing danger and avoiding it.

This can either involve physical danger as during the war when he displayed what some others regarded as cowardice for refusing to come out of a cave for fear the Germans would attack - or political as when he realized that Stalin's attempt to reassert control over the Yugoslav Communist Party in 1943 was a threat to his personal power. It is his ability to survive a string of such incidents, combined with knowing how to play one enemy off against another and outlive them all, that has left him in the unique position of being able to progress from one world capital to another and he assured of a warm welcome in each.

Of course Marshal Tito is well aware that the smiles of some of the welcoming parties and the reassuring phrases of some of the official communiques at the end of his visits conceal hidden dangers. As the recent memoirs of a Yugoslav ambassador in Moscow make clear, there is still a deep suspicion here of the intentions of the Soviet Union towards Yugoslavia, particularly after Tito's death.

It is here that the president's visit to Washington, like his journey to Peking last September, has a very practical purpose. Ties with China and the United States are valued as a counterbalance to ties with the Soviet Union and as a sign of Yugoslavia's determination to have friendly relations with everybody. It is a kind of three-way insurance policy against outside interference.

President Tito's exhaustive foreign tours also bring benefits at home. They demonstrate the prestige of a united Yugoslavia to a people who less than 40 years ago went through not just a war of liberation, but also a civil war of terrifying dimensions in which there were wholesale massacres of Catholic Croats, Orthodox Serbs, and Moslems. About 1.7 million people are estimated to have been killed out of a total population of some 16 million.

Over the past three decades Tito has created a society which is supported by the vast majority of its citizens, but still excites fanatical opposition from political extremists as varied as Croatian nationalists to pro-Soviet hardliners. The economy is booming, but there are 700,000 people (over 10 per cent of the labor force) unemployed . Most Yugoslavs enjoy a degree of personal freedom, including freedom of travel, unmatched anywhere else in Eastern Europe - but there are still around 300 political prisoners.

Abroad, Tito has won international recognition for a country which at the beginning of this century was the plaything of empires. Nobody has done more to dispel the traditional description of the Balkans as "the tinderbox of Europe." Thanks to Tito, it is an image which hasreceded - but it has not been entirely eliminated.