Based on the references of average aerosol extinction coefficient per unit mass concentration in dry environment and baked aerosol scattering extinction coefficient in wet environment respectively, corresponding the two kinds of aerosol extinction hygroscopic growth factor, i.e. f₁(R_H) and f₂(R_H), had been proposed. By utilizing the hourly data from nephelometer and aethalometer, as well as the coincidental environmental and meteorological data, including atmospheric visibility, relative humidity, NO₂ mass concentration, and PM₁₀ mass concentration, in Chengdu from October 2017 to December 2017, the comparative study on the two kinds of aerosol extinction hygroscopic growth factors was systematically carried out. The results showed that both f₁(R_H) and f₂(R_H) could well characterize the optical effect of aerosol hygroscopicity, and their coefficient of determination was 0.90 (passed the significance test of α=0.01). By multi-model comparison, the quadratic polynomial function was proved to best fit the variation of both f₁(R_H) and f₂(R_H) with relative humidity. The ratio of average f₁(R_H) to average f₂(R_H) increased with the increase of relative humidity. Further research indicated that the significant response of baked aerosol scattering extinction coefficient to the variation of relative humidity was fundamental for the above inconsistency between f₁(R_H) and f₂(R_H).