Xi is the first president to take the oath of office, which commits him "to work for a great modern socialist country that is prosperous, strong, democratic, culturally advanced, harmonious, and handsome".
Chinese President Xi Jinping was unanimously appointed for the second term by Parliament and this time without any term limit on Saturday.
The Chinese president's close political ally, Wang Qishan, has been voted in as vice president.
All 2,970 votes were cast in favor of the 64-year-old Xi who, after a vote by the legislature last Sunday, gained the right to continue in office indefinitely after term limits for the president and vice president were abolished.
"Our Chairman Xi is too great, truly he is too great", said Du Meishuang, a Chinese opera singer and delegate from Chairman Mao's home province of Hunan.
The oaths were also a rare chance for the public to hear Wang and Li speak, even though they have both been key enforcers of Xi's signature policies over the past five years.
Wang received only one vote against, with 2,969 delegates backing his promotion. He helped set up China's first investment bank with Morgan Stanley in the 1990s and also established enduring ties with prominent Wall Street figures such as Henry Paulson.
Wang, born in July 1948, was a member of the Standing Committee of the Political Bureau of the Central Committee of the Communist Party of China (CPC) and secretary of the Central Commission for Discipline Inspection of the CPC from 2012 to 2017.
Mr Xi is expected to expand his long-running campaign against corruption within the party to include all state employees through the creation of a new National Supervisory Commission. Several minister-level appointments were scheduled for Monday, including a replacement for retiring central bank chief Zhou Xiaochuan and the head of a new agency to regulate the country's $43-trillion finance-and-insurance sector.
Many were opponents of his "boss", President Xi.
"Xi is already a very powerful man".
The vice-president position has been a largely symbolic role in past decades, but that will not satisfy Wang, who is widely respected for his decisiveness and efficiency, the daily said.