The research on laser scattering characteristics of an object has guiding significance for object detection of lidar. Automated measurement system of laser scattering intensity can be used to build scale model for laser radar cross section (LRCS) and can also be applied to verify theory estimation. The features that SR850 lock-in amplifier (LIA) have,such as high dynamic reserve,lower drift,low distortion,0.001° phase resolution,meet the demand of week signal detection. The transmission of command and data between PC and SR850 LIA is realized to make the system automate. LRCS of typical samples are measured,the method of data processing and the analysis of system performance are also given. The experiment result indicates that the accuracy and dynamic range of the system is improved by the application of SR850 LIA.