Bistatic Surface-Wave Over-the-Horizon Radar (SWOTHR) uses a coast-located array to transmit signals and a ship-carried omnidirectional antenna to receive echoes. In the transmit array

different element utilizes different carrier frequency. The analysis of the direct-path-interference leads to the conclusion that the direct wave is a kind of interference at a position and with a Doppler frequency. Based on the conclusion the interference suppression in time

range-angle and Doppler domain respectively is presented. These three methods for direct wave suppression are evaluated from the aspects of computation complexity

processing gain and output SINR. Finally the simulation and real data results are given to prove the effectivity of these methods.