By using Mie scattering lidar,return signals in cloudy,foggy and sunny weather are measured. In the process of inversion,selection of the logarithmic ratio of aerosol backscatter-to-extinction has a large effect on extinction coefficient. For cloudy weather,when the logarithmic ratio of aerosol backscatter-to-extinction changes from 0.7 to 1.0,the change of aerosol extinction coefficient is 5 times,for sunny weather,the change is near 3 times,whereas for foggy weather,the change is not much. Using visibility data obtained by meteorological observation,corresponding logarithmic ratio of aerosol backscatter-to-extinction is obtained. A new type of method for deciding logarithmic ratio of aerosol backscatter-to-extinction based on weather conditions is proposed. The corrected results are close to the real atmospheric conditions.