The constitutional amendment, the first since 2004, brings the state into line with the charters of the Communist Party and the People's Liberation Army, which do not set term limits for their leaders.
Out of 2,964 ballots, just two delegates voted against the move and three abstained, suggesting minimal opposition to Xi's push to rule for life.
Li Datong, a former top newspaper editor, issued an open letter to the members of the congress calling the two-term limit "the highest and most effective legal restriction preventing personal dictatorship and personal domination of the Party and the government".
The Communist Party, however, controls the legislature and the leadership's proposals are never rejected.
Xi signaled his strength previous year when he had his theories added to the Communist Party charter and he bucked the trend to designate a successor at the end of his first term.
Critics of the move said that China shifted from "one-party rule" to essentially a "one-man rule".
The package of amendments included major provisions to inscribe Xi's eponymous political mantra in the constitution, give the Communist Party an even larger role in the country's affairs and expand the president's anti-corruption campaign.
After taking over a party general secretary, Xi has started a war against the corruption, which helped the country to improve its corruption perception ranking by Transparency International.
Until now, presidents had been limited to two consecutive terms.
His term in office was meant to end in 2023.
Together, the amendments underscore the altered direction China has taken under Mr. Xi.
"In the almost 40 years of reform and opening up, we have successfully established, upheld and expanded the political development road of socialism with Chinese characteristics", Shen said. It included other changes created to put Xi and the party at the very heart of Chinese life.
Shops sell commemorative plates and memorabilia with his image alongside Mao's and he has accumulated so many political and military titles - from president, to Central Military Commission chairman and party "core" - that he has earned the nickname "Chairman of Everything".
"As for the assumptions, conjecture and stretched situations in your question, I think that does not exist", Shen Chunyao said, according to Reuters.
The move is widely seen as the culmination of the 64-year-old Xi's efforts since being appointed leader of the party in 2012 to concentrate power in his own hands and defy norms of collective leadership established over the past two decades.
The amendment offers constitutional support for supervisory commissions, their duties and powers as well as the draft supervision law scheduled to be deliberated at the session, Zheng said.
For India, observers say, Xi's continuation will have particular significance, especially in the backdrop of last year's 73-day-long Dokalam standoff where Chinese troops tried to build a road in the area claimed by Bhutan to reach close to India's narrow corridor connecting North Eastern states. "There was a consensus that we supported him having more time to finish his work", said Dou Yanli, a delegate from Shandong Province.