I don't any of the people who replyed really see the extent of all this. Chinese has many reasons to fear a unified Korea.

1. First a unified Korea could possibly a larger reigional power or maybe a super power. This would lead to a challenge to Chinese dominance in the region. Even if a super power isn't created, a unified Korea would become a much more powerful and larger nation.

2. Second, there is a terroitory dispute between Koreans and the Chinese. Gorgueryeo, an ancient Korean kingdom, is being claimed by the Chinese governement. The kingdom Gorgueryeo occupied all of North Korea and parts of Far North-East China. The Chinese government has made these claims is hopes of keeping the terroitory north of North Korea. The South Korean government has already protested this and stated the kingdom as Korean. A unified Korea would lead to a greater power fighting for that patch of land.

3. Economic power. Korean companies has made great inlands into a developed and international brands. Product quality and reliability is being recognized with Korean companies such as Samsung and LG. If the two Koreas were to unify this would pose a great threat to China. North Korea would offer huge amount of educated, strongly-disciplined cheap labor. Giving Korean companies an edge with high quality and cheap prices. A unified Korea would harm China's economic prosperity as a cheap manufacturer of goods.

This is all a power play people.

Korea has largely been controlled by the super powers and it was the will of the superpowers to split the Koreas. Although a unification is imminent, super powers will try and keep it off as long as they can.