Differential absorption lidar(DIAL) is an effective way to measure the concentration of nitrogen dioxide in extensive air with high precision. Based on the tunable solid-state laser absorption technique, the principle and systematic structure of differential absorption lidar were introduced. The absorption spectra of nitrogen dioxide in the range from 3.410 μm to 3.435 μm were measured with a step of 0.01 nm. The experimental results show that the correlation coefficient between the measured and the simulated absorption spectrum reaches to 92.01% at the standard condition (i.e., 1.0 atm, 25 ℃). Based on the analysis of measured absorption spectrum,the laser wavelength pair which includes the on-line 3.424 μm and the off-line 3.414 μm is determined. In addition, the signal pre-processing and denoising methods were studied. The simulation results show that the concentration errors of nitrogen dioxide can be less than ±0.1 mg/m3 within 1 km by combining the signal pre-processing and the multiple autocorrelation.