In Forward-Looking Airborne Radar (FLAR), the covariance matrix of the Cell Under Test (CUT) is not accurately estimated which is caused by the range-dependence problem, and it declines the clutter rejection performance of the Space-Time Adaptive Processing (STAP). The space-time interpretation method is one of the interpretation methods which can handle the range-dependence efficiently, however, it requires huge computation load, and brings great challenge to the real-time processing of this method. This paper proposes a space-time separated interpretation method. The proposed method makes the space-time interpretation transform in spatial domain and temporal domain separately. Comparing with space-time interpretation method, the proposed method can reduce the computation load greatly while having a little STAP performance loss. In addition, the proposed method can achieve good performance when the antenna error exists. The computer simulation results show the validity of the proposed method.