In the present paper, a new improved method for measuring NO2 concentration of atmosphere by using differential optical absorption spectroscopy of solar spectrum was reported. The sample solar spectra were collected in Chengdu city and Xiling Mountain respectively by a CCD optical multi-channel analyzer. With the upper atmosphere solar spectrum as the reference spectrum, by fitting the sample spectrum and the reference spectrum using least-square method in five spectrum ranges, the various NO2 concentrations (vertical column density) of 3.1 x 10(16) to 5.8 x 10(16) (molecule x cm(-2)) in Chengdu city and 0.7 x 10(16) to 1.0 x 10(16) (molecule x cm(-2)) in Xiling Mountain were obtained respectively. The NO2 concentrations of atmosphere showed an increasing tendency with the rising temperature.