Xi warmly welcomed the second-in-line to the British throne, making the highest-profile visit to China by a member of the royal family since Queen Elizabeth II and her husband Prince Philip in 1986.
William was met by the Chinese leader on the first full day of a trip which comes as London and Beijing have traded diplomatic barbs over pro-democracy demonstrations in Hong Kong, a former British colony.
But the differences appeared to be put aside as Xi congratulated the 32-year-old prince on the expected birth of his second child.
William said he was looking forward to the remainder of his trip, which will see him visit the commercial hub of Shanghai before heading to an elephant sanctuary in the south-western province of Yunnan.
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"It's been a long interest of mine for many years to come and visit China," he told Xi at the Great Hall of the People in Beijing.
William's visit has been seen as an attempt by Britain to improve top-level diplomatic relations with Beijing.
London is anxious to improve its trade ties with the economic powerhouse.
In a leaked diary, he described China's leaders at the 1997 ceremony as "appalling old waxworks", and he has been accused of deliberately side-stepping formal banquets during Chinese leaders' visits to Britain.
During the 1986 royal visit to China, Prince Philip was overheard by a reporter making one of his most notorious remarks.
"If you stay here much longer, you will all be slitty-eyed," he was quoted as telling a group of British students.
Buckingham Palace has been on a charm offensive towards China, with William issuing a Lunar New Year message in Mandarin ahead of his visit.
"Ni hao - that's as far as I got," he told reporters with a smile, standing in front of the Hall of Supreme Harmony, where coronations were carried out before the Chinese imperial regime was overthrown.