Chinese Vice Foreign Minister Liu Zhenmin summoned the South Korean ambassador to China, Kim Jang-soo, and lodged representations to Kim over the decision, China's foreign ministry said in a brief statement.
Hours after North Korea claimed it had successfully put a satellite into orbit on Sunday, South Korea and the US announced that they would begin talks on the deployment of the Terminal High-Altitude Area Defense (THAAD) battery to South Korea.
The launch is widely viewed as a covert ballistic missile test to advance the development of delivery vehicles capable of carrying nuclear warheads.
Analysts say China's leadership is reluctant to impose tougher sanctions against North Korea because a sudden collapse of the regime could spark a refugee crisis at its border and lead to a pro-US, democratic Korea on its doorstep.
Even before North Korea's fourth nuclear test and the rocket launch, China publicly opposed the deployment of the THAAD battery to South Korea, arguing that it could also target China.
South Korea has refuted China's claim and blamed its neighbor for trying to "influence" Seoul's own security policy.
China's anxiety over the THAAD battery in South Korea has illustrated how difficult it is for South Korea and China to develop common security interests in Northeast Asia, despite their booming economic relations.
Meanwhile, China also summoned North Korea's ambassador, Ji Jae-ryong, to protest the North's rocket launch, the Chinese foreign ministry said in a separate statement.
YNA/MNA