In order to shun the wake vortex hazard and assure the flight security, the technique of wake vortex detection by Lidar was studied. The basic principle of wake vortex detection was introduced, and both the detection mode and the system parameters of Lidar were also given. Based on the designed scheme of wake vortex detection by Lidar, the relationships between Doppler spectrum value and the parameters of aircraft type, flight and environment were studied. The radial velocity distribution law of wake vortex was acquired, and its the Doppler spectrum model of laser echo was built. Moreover, the optimal parameters estimation algorithm was selected for wake vortex characterization. Based on the performed wake vortex detection experiment of A340, both the feasibility of wake vortex detection by Lidar and the validity of parameters estimation algorithm of wake vortex were verified.The research results show that the laser echo created of wake vortex is inversely proportional to the cube of radial velocity, but is directly proportional to the square of circulation.