The wind error of multichannel lidar system is simulated through calculation of atmospheric back-sacttering echo signal and weighted least-square fitting. By comparing the wind errors of four wavelengths of the Nd:YAG laser, two kinds of phenomena are found: when the wavelength is 1064 nm, the wind error is the smallest at all different heights; with the aerosol-molecular ratio descending and finally tending to 1, the statistic error increases sharply, which shows that low aerosol-molecular ratio is quite disadvantageous whatever the signal intensity is.