When the mobile wind lidar is carrying out moving measurement, the cumulation time in every direction is much shorter than that in static measurement, and moreover, the sky background, atmospheric turbulence, mechanical vibration, dark noise and electronic noise of detector can heavily worsen the quality of backscattering signal. As a result, the detection range of wind lidar is greatly limited. Moving average filter and median filter whose operation windows length vary with distance can improve the averaged signal to noise ratio by a factor of 2.8 in the altitude range from 12 km to 15 km, which can effectively expand the detection range.