According to the characteristics of Mie scattering lidar echo signal contaminated by noise in day background light, a de-noising method of wavelets was presented. The daylight direct current component was removed by wavelet transform, and the white noise from background light and electrical noise from detection system were reduced by wavelets soft threshold. To verify the feasibility of the de-noising method, Mie scattering atmospheric lidar echo signal was actually extracted and retrieved, the test results show that the effective detection range can be improved from 2.5 km to 5 km, and the contamination from electric noise and the background light noise can be reduced by the proposed method in measurement of experimentations.