The appointment by the Politburo of the ruling Communist Party of China puts Xi in charge of a commission that will be in charge of "making overall plans and coordinating major issues and major work concerning national security".
The move follows Xi, 60, being appointed in November as the head of a new panel overseeing the country's reforms.
The body, modelled on the lines of the United States National Security Council, consisted of heads of military, intelligence and top homeland security officials.
The NSC leadership is yet another powerful post for Xi, who is also head of the CPC and Commander-in-Chief of the armed forces besides being the president, making him the most powerful leader in the country.
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The commission, which will answer to the Political Bureau of the CPC will be responsible for decision-making, deliberation and coordination on national security work, the document approved by the Politburo today said.
The move to set up the NSC came in the aftermath of the terrorist attack at Tiananmen square here last year in which four persons from restive Xinjiang region were killed.
"The establishment of security will make forces like terrorism, extremism and separatism nervous," Chinese Foreign Ministry spokesman Qin Gang earlier said.