In surgery operations, wound should be cleaned with warm sterilized saline solution. In order to reach rapidly warming the washing solution from the room temperature during the surgery, we designed a thermostatic medical infusion pump. The present paper mainly presents researches on the two temperature control methods in the standby mode and in the flushing mode of the system. In the standby mode, the traditional proportional-integral-derivative (PID) control algorithm was adopted. In the flushing mode, dynamic characteristics of the system was changed in real time, which made the thermostatic control process more complex, and the fitted control function combined with the PID control algorithm was adopted in this mode. The temperature control parameters were adjusted in real time according to the initial temperature and the flow rate of the washing solution to obtain a constant temperature of the washing solution, no matter how the initial temperature and the flow rate are changed. The experiment results showed that this kind of control system performed well with a high accuracy.