Abstract: ‍ ‍Compared with the traditional airborne phased array radar single input multiple output system， the space time adaptive processing （MIMO-STAP） technology in the multiple input multiple output radar can greatly improve the performance of clutter suppression and moving target detection. However， traditional MIMO-STAP requires a large amount of computation and training samples， which cannot meet the requirements of non-homogeneous clutter environment and real-time processing. In order to solve this problem， this paper proposes a space-time adaptive clutter suppression method for airborne MIMO radar， namely CSBSM method. This method makes use of the low rank property of the clutter covariance matrix， constructs the clutter covariance matrix based on the space-time sampling matrix， and estimates the clutter power through subaperture smoothing. In the non-uniform clutter environment， CSBSM only needs a single sample to effectively suppress clutter. At the same time， since the space-time sampling matrix and the position of independent sampling points can be calculated offline， the CSBSM method requires less computation and is suitable for extremely non-uniform clutter environments. Computer simulation results verify the effectiveness of the proposed method.