The optical property of atmospheric aerosol in Nangjing is inversed, and the different factors which can influence the inversion accuracy of extinction coefficient of atmospheric aerosol are studied. The de-noising processing for signal is carried out by different methods，and the suitable de-noising method is found. The reprocessing for de-noised signal is carried out with five-point triple smoothing, wavelet de-noising and eleven-point smoothing respectively, and the method which can obtain accurate inversion result is chosen. The effects of logarithmic ratio of backscatter extinction and extinction coefficient at the reference height on the inversion result of Klett method are analyzed. The inversion results when k ranges from 0.67 to 1.0 and σm is about 1×10-5 km-1 are analyzed. The influence of the lidar ratio on the inversion result of Fernald method is analyzed when the lidar ratio ranges from 20 to 70. The results of Klett method are compared with that of Fernald method. It is found that in the region with low atmospheric aerosol content, the results of the two methods are different, but the results of the two methods are almost same in the region with high aerosol content.