Abstract: For the issue that escort jamming in main-lobe can not be countered by radar, a main-lobe jamming suppression technique about multistatic radar is studied, and the Adaptive Main-lobe Jamming Cancellation Algorithm based on Block Preconditioning (BP-AMJCA) is proposed in this paper. Firstly, block preconditioning is combined with direct matrix inversion to get the initial weight vector, then High Order Cumulants is introduced to Variable Forgetting Factor Recursive Least Square (HOC-VFF-RLS) Algorithm to realize the update of weights. Compared with traditional Adaptive Main-lobe Jamming Cancellation Algorithm based on Least Mean Square (LMS-AMJCA), the proposed algorithm has little complexity increase, fast convergent rate and good robustness. The simulation experiment result of main-lobe jamming suppression shows that the issue of target echo signal cancellation in main-lobe is solved, and the output SINR of two receivers is improved to 35-40 dB by BP-AMJCA algorithm, which has important application value.