A circuit topology based on six-port network is presented, which can be adopted to effectively suppress the leakage signal. This six-port network is mainly composed of three 3 dB hybrid couplers and an unequal Wilkinson power divider. Among the two output ports corresponding to the receiving signals, two leakage signals of the transmitting antenna are offset each other for their equal-magnitude and out-of-phase, which is benefit to achieve a high level of transmitting(Tx)-to-Rx isolation in the radar network. In order to demonstrate the Tx leakage canceller, a circuit topology is designed and simulated from 22 GHz to 26 GHz. In the operating band, the isolation of the Tx leakage canceller is lower than -29.5 dB, and it achieves the maximum isolation -44 dB at its center frequency. As shown, the circuit topology efficiently improves the isolation of single-antenna radar system and performs cancellation for the Tx leakage power.