The live-fire drills will last for four days, and are being conducted just off the coast of North Korea in a show of strength amid world war 3 fears.
An area spanning 276 square kilometres has been declared off-limits to all but military vessels during the intense drills.
The scale of the drills, including how many ships are participating, is not clear.
Chinese warships also took part in a major drill in the East China Sea last week, while its air force has also conducted high-level drills.
The US, South Korea and Japan also held joint military exercises this week in a show of strength designed to put pressure on North Korea.
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The three nations teamed up in the hope of persuading North Korean dictator Kim Jong-un to abandon his aggressive programme of nuclear missile testing.
However Kim responded with further threats of nuclear war.
Pyongyang branded Trump administration plans to impose a naval blockade on the state “extremely dangerous”.
It said cutting North Korea off would be another “big step” towards nuclear war, as the flurry of military activity continued.
The US has responded to North Korean aggression with aggression of its own, holding huge military drills throughout East Asia, and using incendiary language that has riled Kim Jong-un.
As China holds its own tests, it could be a sign its attitude has come still closer to that of the US.
However one expert says China’s own instincts could be the key to resolving the crisis.
Joshua Pollack, editor of The Nonproliferation Review and a leading expert on nuclear proliferation, says showing “willingness to negotiate” with Kim Jong-un would be the first step to cooling the heated conflict. China’s attitude to North Korea has tended to come closest to this.
However he says US pressure on China could make matters worse – as it is forcing president Xi Jinping to move his stance more in line with firebrand Donald Trump.
Mr Pollack told Express.co.uk: “The Trump Administration definitely sees China as the key to the problem, since it is responsible for the overwhelming majority of North Korea’s known, licit trade with the outside world.
“The White House demands that China should cut off the country entirely. Chinese officials are reluctant to go that far.
“Instead, they keep pressing the Americans to ease some of the military pressure on North Korea by suspending major combined exercises in exchange for a suspension of missile and nuclear tests — the so-called “freeze for freeze” proposal. The Administration has rejected this idea out of hand.”
China’s more conciliatory stance, if it can persuade the US to join it, could be the key to calming Kim Jong-un and minimising the threat he poses to the rest of the world.