To improve the measurement accuracy of laser radar cross section (LRCS), the background scattering existing in the measurement is pointed out. The equation for measuring LRCS is presented. The mechanism for the effects of the background scattering from the ground and supporting frame on the measurement accuracy was analyzed. According to the equation and the mechanism, the methods to reduce the background scattering, which include extinction material coating, multi-contrasting measurement, size matching, are put forward. The method of the extinction material coating was verified by experiment. The experimental results show that the method could effectively reduce the background scattering and improve the measurement accuracy.