Object's radial velocity effect on object’s radar cross section (RCS) outdoor measurement with pulse to pulse frequency shifting radar was researched. The cause of object's radial velocity make RCS measurement results inaccurate were analyzed from the aspects of object-imaging's position shifting and profile distortion. The numerical relationship between the velocity and RCS measurement error was presented using computer simulation. A method to reduce the RCS measurement error was presented base on these analysis. A method to correct the object's velocity effect was discussed bases on the architecture that the two-channels radar can measure the target on two different frequency band in the same time. The method was used to deal with the measurement data of BHEML-1 radar and the results were analyzed and compared.