A new method of using two-wavelength Mie-depolarization lidar for remote sensing extinction hygroscopic growth factor of aerosol near ground layer under varying conditions of relative humidity(RH) is proposed. Based on the algorithm used in lidar vertical aerosol hygroscopic growth observations, lidar horizontal measurements data is researched using strong correlation between extinction coefficient and RH, and the measured particle mass concentration going along with the decrease of depolarization ratio is used as a criterion, which proves that the hygroscopic effect of aerosol is the main cause of the extinction coefficient increment. Compared to the lidar vertical aerosol hygroscopic growth observations method, the proposed method has the advantage of the raising data selection criterion and simple meteorological conditions. Extinction hygroscopic growth factor can be calculated using valid data in lidar database, and its wavelength dependence is analyzed. Observation results at Hefei district show that, in various natural atmospheric environments, unimodal, bimodal and even multimodal aerosol distributions may exist. As a result, positive correlation, negative correlation and irrelevance between RH and Angstrom exponent can be observed, and hygroscopic growth factor at short wavelength can be weaker than, stronger than or equal with that at long wavelength.