China has been concerned with North Korea lately. It would prefer North Korea not upset other countries with its actions. China also opposes the invasion of South Korea by North Korea. If an invasion were to take place, it would put China in the position of having to either support or condemn North Korea for its actions. China does not want a role in the affairs of this insignificant country because it does not want to be looked down upon by the UN for choosing sides.
China views Sudan as nonessential.
There are little interests concerning China. Therefore, the concern for the Sudan is minimal. In dealing with this issue, China will follow the Security Council majority decision or abstain. Voter registration disputes to this day have delayed the referendum. China holds that internal conflict should not be dealt with by the UN, but rarely uses the veto as a way of obstructing the effort.