The Russian military has compared the show of force to the USSR's 1981 war games, in which as many as 150,000 Warsaw Pact soldiers took part in "Zapad-81" (West-81).
The worldwide military exercise, named Vostok-2018, will involve 300,000 soldiers, 36,000 military vehicles, 1,000 planes and 80 warships, according to Russian defence minister Sergei Shoigu.
Amid growing recent tensions between Moscow and the West, NATO has said it will monitor the drills closely.
The People's Liberation Army, China's military, was "still in the process of acquiring combined arms training and expertise as it transformed into an informationised and modern fighting force", he said.
Russian S-300 and S-400 air defense missile systems are put in combat mode to practice hitting targets in the largest military drill the nation has held since the 1980s.More news: FDA mulls ban on flavored e-cigarettes
"China, by sending a PLA [People's Liberation Army] element to train with the Russians, is signaling that USA pressure is pushing it towards much closer military cooperation with Moscow".
"It fits into a pattern we have seen over some time - a more assertive Russian Federation, significantly increasing its defence budget and its military presence", said the alliance's spokesman Dylan White.
Speaking of the forum, Jinping said the two countries "friendship is getting stronger all the time".
Hong Kong-based commentator Song Zhongping said China is anxious to acquire more experience in large-scale operations that might become a factor in a conflict with the US and others over territorial claims in Asia.
Russian Defence Minister Sergei Shoigu said the war games were one of the biggest ever staged, with 300,000 soldiers, 36,000 military vehicles, 1,000 planes and 80 warships involved.More news: Death Toll Rises To 32 In Nangarhar Explosion
Maintaining Russia's defence capabilities is "justified as rival powers are frequently quite aggressive and unfriendly", Kremlin spokesman Dmitry Peskov said in August in comments carried by state news agency, TASS.
"The war games have laid a foundation for China and Russian Federation to enhance cooperation on worldwide arena and will lift the combat proficiency of both sides", he said.
"These are very important drills but they are part of routine annual work to develop the armed forces", he told journalists.
Russia's defence ministry hailed the drills as successful.
Since then Moscow has increased the number of its large-scale military exercises in the Caucasus, the Baltic and the Arctic.More news: Apple could unveil biggest iPhone ever Wednesday
Russian Federation showcased its most sophisticated air defence system on Wednesday, using it to repel a mock attack from the sky as part of what it describes as its largest-ever military drills.