The narrow emission spectrum of light emitting diode(LED) limits differential optical absorption spectroscopy(DOAS)retrieval range, and it is not easy to realize simultaneous measurement of various gases. In this paper, two kinds of ultraviolet LEDs are combined to form a combined LED broadband light source, which is applied to DOAS to simultaneously detect atmospheric SO2 and O3. The spectral analysis shows that their spectrum is superimposed in 280~295 nm and has an obvious lamp structure in 275~301 nm. The structure enhances and drifts to the shortwave direction with the increase of the dual-peak light intensity ratio. During actual measurement, the LED spectrum will change independentlydue to the environmental conditions. Moreover, atmospheric extinction is different in their emission spectral bands. Therefore, the dual-peak light intensity ratio ofthe atmospheric spectrum will change continuously and is inconsistent with the lamp spectrum. It is not easy to offset the lamp structure by dividing the two.The spectrum retrieval results show that the combined lamp structure as a reference spectrum can not fit well with the interference structure. In order to remove the influence of independent LED spectrum changes on spectrum retrieval during measurement, it is proposed to use each LED lamp structure as a reference spectrum to participate in the fitting. The fitting residuals of SO2 and O3 are reduced from 1% and 6‰ to about 4‰, respectively, and the interference structure is well removed.Compared with evading interference structure, the retrieval range of SO2 and O3 is broadened, and the number of SO2 and O3 absorption peaks in the retrieval range is increased by 1.75 and 1 time, respectively. The average fit errors of SO2 and O3 are reduced by 67.5% and 37.3% respectively. The measurement accuracy is significantly improved. The measuremens are compared with the SO2 and O3 levels measured by the traditional xenon lamp long path DOAS system. The comparison shows excellent agreements with Pearson correlation coefficients (R) of SO2 and O3 measurements above 95%. The results demonstrate that the lamp structure of a combined LED broadband light source can be fitted by the independent lamp structure of each LED in DOAS retrieval.