There are two problems about test system of pump: low measurement accuracy of NPSHr for opened system and overheating of high power pump for closed system. According to above problems, the design and control method for a new opened-closed test system of pump is proposed in this paper. Acquisition, display, processing, automatic adjustment, correction and print of test data can be finished in this system. The system can work more stable and reliable. Its measurement accuracy was improved greatly by equal-flow adjustment of water tank.