China is sending 3,200 troops to take part in "Vostok-2018", with many Chinese armoured vehicles and aircraft. Mongolia is also sending some units, reports BBC.
The last Russian exercise of similar scale was in 1981, during the Cold War, but Vostok-2018 involves more troops.
The week-long manoeuvres come at a time of heightened Nato-Russia tensions.
As the exercises began, Russian President Vladimir Putin met his Chinese counterpart Xi Jinping at a forum in the eastern city of Vladivostok and told him "we have a trusting relationship in the sphere of politics, security and defence".
Relations between Russia and Nato - a 29-member defence alliance dominated by the US - have worsened since Russia annexed Crimea from Ukraine in 2014.
Kremlin spokesman Dmitry Peskov said the drills were justified given "aggressive and unfriendly" attitudes towards Russia.