Abstract: Aerosol complex refractive index is one of the most fundamental optical parameter, which can directly relate to aerosol properties such as scattering and absorption index. In this study, we retrieved the aerosol complex refractive index using an inversion method with fine resolution for time series. Based on high precision measured size distribution of aerosol, aerosol scattering and absorption coefficients, the aerosol complex refractive index was retrieved using the Lorenz-Mie scattering theory. The results indicated that:(1) In the urban area of Tianjin City in April 2011, the real part of averaged equivalent complex refractive index of the aerosol at the wavelength of 0.55 μm was 1.64, and the imaginary part was 0.015. (2) An obvious daily variation regularity of aerosol complex refractive index is found in this study. Both the real part and imaginary part of complex refractive index were significantly positively correlated with relative humidity, and were negatively correlated with wind speed. (3) The contributions of different scale aerosol to total extinction coefficient were calculated, it showed that 86% of the scattering coefficient is from the small aerosols with radius >0.25-1.00 μm. Meanwhile, the aerosols particles with radius from 0.25 to 2.50 μm and from 2.50 to 32.00 μm contribute 53% and 47% to the total absorption coefficient, respectively. Studies had shown that aerosol particles >0.25-1.00 μm and particles >1.00-32.00 μm have similarly higher contribution rate to the absorption coefficient, but for the scattering coefficient, aerosol particles with a contribution rate of >0.25-1.00 μm are higher. Based on comprehensive consideration of aerosol scattering coefficient, absorption coefficient and extinction coefficient, controlling aerosol particles >0.25-1.00 μm can effectively improve atmospheric visibility.