Abstract: Bistatic MISO surface-wave radar uses an array located along a coast to transmit the FMICW signals of multiple carrier frequencies and uses a single antenna to receive the returns.The range-azimuth coupling occours due to the fact that the carrier frequency at each of the transmit elements is different one another.For serious coupling,the space-time supresolution method doesn’t work.The coupling is deduced based on the amplitude comparison monopulse and the coupling coefficient is obtained,which is dependent on both the carrier frequency an antenna emits and the position it locates.The problem of selecting the optimum frequency code for range-azimuth decoupling is solved by the genetic algorithm and the resultant measurment accuracy is improved greatly.The computer simulation proves that the decoupling can be solved by proper permutation of the carrier frequency.