Abstract: Dense repeater jamming not only causes false alarms, but also raises the threshold of constant false alarm ratio detector nearby the jamming, which degrades the performance of targets detection. On the other hand, the samples contaminated by jamming degrade the performance of space time adaptive processing. To deal with these issues, a method to suppress dense repeater jamming is proposed. Firstly, the directions of the jammers are estimated. Secondly, Generalized Sidelobe Canceller (GSC) is used to cancel the jamming in the spatial domain. The auxiliary channels of the GSC are the sum beams pointing at the jammers, and the covariance matrix of the GSC is estimated with the jamming samples selected from the clutter free region. The proposed method reduces the false alarms caused by the dense repeater jamming, and improves the performance of targets detection. In addition, the structure of this method is simple and easy to realize. Simulations are presented to verify the effectiveness of the proposed method.