A new technology of NO2 concentration measurement based on the non-dispersive optical method is studied. On the basis of intensive absorption of NO2 in the ultraviolet-visible waveband, and according to the Lambert-Beer’s law, the concentration of NO2 can be derived by the relation curve of gas absorption rate and concentration calibrated in advance. The spectrometer, xenon lamp and a series of standard sample gas were used in the laboratory experiment. Four wavebands of 5 nm bandwidth were abstracted from the spectral data of 290～410 nm from spectrometer measurement; the absorption rates of different concentrations were calculated, and the polynomial fitting with gas concentration was made. The fitting correlation coefficients in different wavebands and fitting orders were compared, the best waveband and fitting order were obtained, and the selection basis of filter was provided.