The director-level defense talks are held every year, but were completely overshadowed this time around by the North's fourth nuclear test last week, which triggered global condemnation and the promise of fresh UN sanctions.
"China expressed its willingness to take part in adopting a UN Security Council sanctions resolution," the head of the South Korean delegation, Yoon Soon-Ku, told reporters afterwards.
"China reiterated that it thoroughly rejects the North's nuclear development and nuclear testing," Yoon was quoted by AFP as saying.
The talks came two days after South Korean President Park Geun-Hye urged China to step up to the plate and support genuinely punitive sanctions that would help bring Pyongyang to heel.
"I believe China is aware that if its strong determination is not put into actual, necessary actions, we will not be able to prevent a fifth or sixth nuclear test," Park said.
China is North Korea's chief diplomatic protector and economic benefactor, but traditional ties have become strained as Beijing's patience has worn thin with Pyongyang's behavior and unwillingness to rein in its nuclear weapons ambitions.
North Korea says the January 6 test was of a miniaturized hydrogen bomb -- a claim largely dismissed by experts who argue the yield was far too low for a full-fledged thermonuclear device.
But whatever the nature of the device, it was North Korea's fourth nuclear test since 2006, and further evidence of Pyongyang's intention to continue developing its nuclear weapons capability in the face of international censure.