In the background of rapid growth of patent application and quick technology innovation, most countries’ patent systems are facing increasingly serious challenge of patent grant delay, China as well. This paper has analyzed the influencing factors of China’s invention patent examination period by using the method of survival analysis and China’s invention patent data in 2003, and discovered that the protection factors affecting time-lag of China’s invention patent grant include the number of IPC, the number of patent citation and origin country of patent application, while the number of patent claim is a hazard factor. Therefore, this paper has proposed many measurements including to establish the duty of exactly defining IPC, to raise the level of citation and additional fee of the claims and to implement differentiated political propensity for improving performance of China’s patent examination system.