In order to study the application of dual-frequency lidar in the detection of hypersonic target, the absorption and attenuation characteristics of laser in plasma were analyzed theoretically. Based on the measured data of RAM-C experiment, the plasma electron density of blunt body model in different hypersonic flight scenarios was obtained by simulation calculation, which verified the accuracy of the calculation. The temperature distribution on the stationary line of blunt body was calculated from 8 000 K to 16 000 K, and combined with theoretical analysis we can obtain laser attenuation in plasma sheath on electron density, temperature and laser frequency, which showed that the absorption of laser by plasma sheath was very small. By comparing the echo signal to noise ratio of dual-frequency laser and single frequency laser in turbulent transmission, the anti-turbulence characteristics of dual frequency laser were obtained. Thus shows that the dual-frequency lidar is an effective way to detect the hypersonic target.