Since the sidelobe produced by a source node can interfere with other unintended base stations in wireless sensor networks（ WSNs）. Present a sidelobe supression algorithm which can decrease interference with unintended base stations by selecting suitable relay nodes that can control interference noise ratio（ SINR） of signal received by unintended base stations below the threshold value. Simulation results show that the algorithm can effectively reduce sidelobe level at directions of unintended base stations and improves SINR of system.