BEIJING (AP) _ ''I know this guy 3/8'' exclaimed President Bush as he reached out Saturday to shake a Chinese hand in the crowd that welcomed his return to Beijing.

Bush's visit with his wife, Barbara, seemed one part diplomacy, three parts nostalgic homecoming.

It was the president's fifth trip to China - and his wife's sixth - since he represented U.S. interests here as a special envoy in 1974-75, after President Nixon reopened Sino-American contacts but before formal diplomatic relations were restored.

The Bushes were clearly glad to be back, and Chinese officialdom seemed pleased to have them.

''We're happy you're in China. We warmly welcome you,'' President Yang Shangkun told Bush over toasts in the Great Hall of the People. ''Every time you came you tried to solve major issues.''

From the airport, Bush rode directly to Tiananmen Square, where the ancient imperial Forbiddden City sprawls on one side of an eight-lane highway and the mausoleum of Chairman Mao Tse-tung the other.

Bush ordered his stretch Mercedes limousine stopped and he jumped out to work the crowd.

''I know this guy 3/8'' Bush called out, using one of a politician's favorite salutations in a crowd. ''Good to see you all again 3/8''

The Chinese clapped, politely. Metal barriers held the citizenry back. Several thousand bicyclists and pedestrians lined the street along the motorcade route, but local Americans said many were there not to see Bush but simply because traffic had been halted.

It doesn't take much to create a crowd in Beijing, they said. All you have to do is stop traffic for five minutes.

Bush's stop, planned in advance, was outside the Gate of Heavenly Peace and below a massive portrait of Mao Tse-tung. American flags flew beside Chinese flags in red with five gold stars. Some in the crowd waved tiny American flags.

A government interpreter in a leather coat was asked how the American flag happened to be flying there. ''Ask the American embassy,'' she replied.

Someone held aloft a small white sign that read ''Hello.''

''How are you?'' said Bush, reaching for hands. ''So nice to see you.''

''It's warm here, warmer than I remember,'' he said.

A hazy red sun hung low in the afternoon sky.

Mrs. Bush, in a purple coat, seemed to be enjoying the moment, too. ''I love China,'' she said on the plane from Tokyo. ''I had very, very happy years there.''

The first time they were in China was like seeing ''a black and white movie,'' she said. ''Last time we were there, three or four years ago, it was really an emerged nation.''

Next stop was the Diaoyutai State Guest House, where Premier Li Peng and tea awaited. Also gifts.

Li remembered that the Bushes were fond of bicycling around Beijing when he was head of the U.S. Liaison Office here. So he gave them two bikes, one in lime green for Bush, a bright red one for Mrs. Bush.

''What a beautiful present,'' Bush said. An aide handed him a large, gold- wrapped box which Bush gave to Li. ''This is not nearly as nice,'' the president said apologetically.

Li handed the box to an aide who unwrapped it. The premier seemed stunned by his gift, a pair of black cowboy boots. They were handmade in Houston, with a Chinese flag on the front of one boot and an American flag on the other boot.

Ling said maybe he would wear the boots when he visited America. ''It's not a habit in China to have flags on the front,'' he said.

There was an untold secret about the Bushes' gift of a pair of Flying Pigeons, made by the Tianjin bicycle factory which turned out China's first bikes and is a major producer.

What went unmentioned was that the Xinhua News Agency reported last Tuesday that Li Qizhu, a top executive of the bicycle factory, had been charged with taking a $13,500 bribe for illegal shipments of 11,000 bicycles and with profiteering on the sale of another 600 bikes.