Signal spectrum in rocket's power line was analyzed and found that it had only low-frequency component that used to provide rocket's power, other frequency components were idle, and utilization of frequency spectrum was low. On this basis, the distributed circuit models of rocket's power line were established, the attenuation and crosstalk characteristics of it were obtained through analyzing the circuit model, the method of information setting by collineation on the precision-guided rockets using the idle frequency was proposed. The results of filed test show that this method could achieve reliable setting, low cost of renovation without changing existing rockets launching platform, which could meet the needs of precision-guided rockets setter, the rate of its information setting can reach 6 KB/s.