The axial force is an important index of rotating machinery, and real axial force can only be obtained through practical measurement in the operation. Some problems related to axial force measurement of water pump is studied in the paper and a special measurement device is designed. The data of real axial force vs. flow are measured during the pump operation and a measurement curve is sorted out by use of reasonable axial force transfer structure and optimized force measuring element. The relative non-linearity error of the measurement device is less than 0.3FS by calibration. The actual measurement results of axial force are consistent with the theoretical curves.