In this paper a method called ‘amplitude ratio weighted coherent cancelling (ARWCC)’ is proposed, which has the ability of rejecting the main-lobe jamming within one PRI of bistatic radar system (BRS). The advantage of BRS in main-lobe jamming rejection is analyzed firstly. Secondly, the technical mechanism and implementation procedure of conventional methods are discussed which contain the wiener filter, the amplitude ratio feature clustering (ARFC) and coherent cancelling (CC), etc. The proposed ARWCC has two key features. The first one is that it has no special assumption for detect probability $P_{d}$ (ARFC assumes that $P_{d}$ should be equal to 1), while second one is that it adopts weighted coherence cancelling instead of direct subtracting (CC adopts direct subtraction). The ARWCC contains 5 steps: aligning, match filtering, calculating weight coefficient, weighted coherent cancelling, pulse compressing and eliminating secondary targets. The ARWCC is suited to detect the small targets specially in the background of false target deceptive jamming (FTDJ) and the smart noise jamming with frequency shift (SNJ-FS). The effectiveness of the ARWCC is confirmed by simulations.