The invention relates to a high-pressure injection system for injecting a contrast agent to human tissue or organs and a using method thereof. The high-pressure injection system comprises a main machine located at the first using occasion, a needle cylinder detachably connected with the main machine and an extension pipe detachably connected with the tip end of the needle cylinder, and the high-pressure injection system further comprises pre-filling equipment located at the second using occasion. According to the structure of the high-pressure injection system and optimization of the using method, the pre-filling equipment is adopted in the second using occasion for performing medicament filling on the needle cylinder, so that the operation time of medical workers in the first using occasion is greatly shortened, the working intensity of follow-up workers is relieved, the utilization rate of image documentation equipment is increased, and the medical care service quality and inspection safety are improved.