The measurement of radar cross section (RCS) is of great significance to reduce target RCS and the probability of target being detected by radar. This paper describes the measuring principle and system composition of RCS. First, the composition and measuring principle of RCS measuring instrument system and calibration system are introduced in detail. Secondly, the measurement error of the system is analyzed, and the RCS data processing method is proposed. Finally, the target is tested, and the curves of the target in different pitching angles and polarization directions at the frequency point of 0.8GHz are obtained, and the mean value of the RCS measurement results is calculated.