In many cases non-cooperative things that have no available ID numbers need to be identified via electromagnetic sensing. In order to obtain target's accuracy Radar Cross Section (RCS) character, separating target signal from background is a necessary step in RCS measurement of heavy targets mounted on a metal pylon and both geometric fit and algebraic fit can be applied in the separation procedure. In this paper, the feasibility of Kasa method in separation of target signal and background signal is researched. The bias of Kasa method under whole circle circumstance is deducted, and the validation of simulation data using Kasa method has been accomplished. The separation result of two measurement data is compared between Kasa method and ODR (Orthogonal Distance Regression) method, and the comparison result shows that Kasa method can be used in separation of background and target signal.