The Tiananmen Square event to mark 80 years since Japan's defeat at the end of World War Two, has been largely shunned by western leaders with Putin and Kim - pariahs in the west due to the Ukraine war - the guests of honour.
Designed to project China's military might and diplomatic clout, it also comes as U.S. President Donald Trump's trade tariffs and volatile policymaking strain its relations with allies and rivals alike.
"Today, mankind is faced with the choice of peace or war, dialogue or confrontation, win-win or zero-sum," Xi told a crowd of more than 50,000 spectators, adding that the Chinese people "firmly stand on the right side of history".
Wearing a suit in the style of those worn by former leader Mao Zedong, Xi earlier greeted the more than 20 leaders saying "Nice to meet you" and "Welcome to China" in English. Indonesia's president, facing widespread protests at home, made a surprise appearance.
"Please give my warmest regards to Vladimir Putin, and Kim Jong Un, as you conspire against The United States of America," Trump said in a post on Truth Social as the parade kicked off.
Trump had earlier told reporters he did not see the parade as a challenge to the United States and reiterated his "very good relationship" with Xi.
The 70-minute showcase featured aerial displays, marching troops as well as cutting-edge military equipment such as hypersonic missiles, unmanned drones and outfitted tanks. Xi will review the troops lined up in formation before delivering a keynote speech.
Major roads and schools have been closed in Beijing for the parade, the culmination of weeks of painstaking security preparations and midnight rehearsals.
Xi has cast World War Two as a major turning point in the "great rejuvenation of the Chinese nation", in which it overcame the humiliation of Japan's invasion to become an economic powerhouse.
Earlier this week, Xi unveiled his vision of a new global order at a regional security summit, calling for unity against "hegemonism and power politics", a thinly veiled swipe at the United States and Trump's sweeping tariffs aimed at both friend and foe.
Putin has already used the occasion to seal deeper energy deals with China, while the gathering offers Kim an opportunity to gain implicit support for his banned nuclear weapons.
Kim, debuting in his first major multilateral event, will become the first North Korean to attend a Chinese military parade in 66 years.
Nothing has been left to chance for the milestone gathering.
Local governments nationwide have mobilised tens of thousands of volunteers and Communist Party members to monitor for any signs of potential unrest ahead of the parade, estimates based on online recruitment notices show.
with AP
