"Seventy years ago on this day, Comrade Mao Zedong solemnly declared here to the world that the PRC was founded and the Chinese people had stood up," Efe news quoted Xi as saying from the balcony on the Gate of Heavenly Peace in front of Tiananmen Square.
On October 1, 1949, Mao Zedong, or Chairman Mao, announced the formation of the PRC, after communist forces won a bloody civil war.
"There is no force that can shake the foundation of this great nation," he said amid applause from thousands of people seated in the stands set up for the anniversary celebrations. "No force can stop the Chinese people and the Chinese nation forging ahead."
Xi said that the Chinese people have made great achievements over the past seven decades that have amazed the world on account of being united.
"On our journey forward, we must uphold the principles of 'peaceful reunification' and 'one country, two systems,' maintaining lasting prosperity and stability in Hong Kong and Macao," he stressed.
Xi also called for the country's "complete reunification" in reference to the island of Taiwan, which it considers part of its territory and from which it has recently wooed away another two diplomatic allies.
The Asian giant's leader said that China's present was being created by hundreds of millions of Chinese people, adding that "China will surely have an even brighter future".
Xi's shorter-than-expected speech gave way to a military parade - the largest in China's history.
On display at the parade were some of China's finest military equipment including the JL2 missile which can be launched from the country's Jin class submarines, tasked with mounting seaborne deterrent missions and helping to ensure second strike capability, the BBC reported.
The DF26 anti-ship ballistic missile was also on show. It can carry either a conventional or nuclear warhead.
This is dubbed a "carrier killer" and designed to prevent an intervention by the US in military theatres of strategic importance for China (like the South China Sea).
Some of the other equipments were the latest road-mobile DF-41 intercontinental ballistic missile, which Chinese analysts have said is able to target any part of the globe; and the stealthy batwing-shaped Sharp Sword drone, designed to be launched from aircraft carriers.
According to the Ministry of National Defence, around 15,000 military personnel, 580 pieces of military equipment and 160 aircraft made an appearance at the parade.
For the first time, a contingent from China's 8,000-strong UN peacekeeping standby also participated.
During the parade, 70,000 balloons along with 70,000 pigeons were released over Tiananmen Square, while 56 guns were fired to represent the number of different officially recognised ethnic groups in China.
Later in the evening, a gala performance will be held in the square.
( With inputs from IANS )