Abstract: Non-sidelooking array configuration leads to heterogeneous airborne radar echo data, it degrades seriously the clutter suppression performance of the traditional Space-Time Adaptive Processing (STAP) algorithms. To solve this problem, a heterogeneous clutter suppression method, which is robust to array error, is proposed. Firstly, a clutter representation basis is constructed based on a priori information such as system parameters. Then, the test data is fitted in an iterative least square manner with consideration of array error, and the closed-form solution is derived and utilized here. Finally, pulse Doppler processing and constant false alarm detection are conducted on the residual data. The proposed method does not need any training sample and can effectively suppress the heterogeneous clutter for airborne non-sidelooking radar without elevation degree of freedom. Simulation results verify the validity of the proposed method.