The invention discloses a method for controlling medical fluid injection. An operating method used for contrast agent injection system comprises: starting an injection rules including the desired flow speed of contrast agent and adjusting the actual flow speed of the contrast agent to follow the desired flow speed of the contrast agent at least partly based on the inherent system elasticity of the injection system. An operating method used in medical imaging system including a medical fluid injection assembly and a medical imaging apparatus comprises: starting an contrast agent injection rules corresponding the desired level of patient enhancement and adjusting the actual flow speed of the contrast agent injection rules to obtain the desired level of patient enhancement at least partly based on the inherent elasticity of the injection assembly. The invention urges the actual injection flow speed of medical fluid to be basic consistent with the desired flow speed.
