Highprecision radar cross section (RCS) measurement has high requirement for background environment. It is difficult to eliminate the clutter effect through background vector cancelling when strong interference exists in background environment. This paper proposes a high accuracy RCS measurement method based on imaging extraction to separate and extract the target scattering signal from background clutter, thereby the measurement accuracy is improved. Firstly, the mathematical relationship between the image and RCS is derived, then the echo measured in the revolving stage mode is utilized to conduct the imaging processing and obtain the 2D image of the target area. Then, the 2D image of the target is extracted from the imaging area, and the RCS of the target is obtained through spectrum transform and calibration. The simulation results show that in RCS measurement under interference the proposed method can improve the measurement accuracy by 3~5 dB, and measure the target with weak scattering. Experiment results show the effectiveness and accuracy of the imaging extraction method.