Near-infrared diffuse reflectance spectroscopy (NIRDRS) has been proven to be a convenient and fast quantitative method for complex samples. A method for simultaneous quantitative determination of phenol and p-nitrophenol in wastewater was developed by using NIRDRS with a preconcentration procedure of resin adsorption. In the method, the analytes were firstly adsorbed onto the adsorbent, and then the NIRDRS spectrum of the adsorbent was measured for quantitative analysis by partial least squares (PLS) regression. The results show that the two phenolic compounds can be immobilized onto the adsorbent and directly measured by NIRDRS. The correlation coefficients (R) between the reference values and prediction results for phenol and p-nitrophenol were 0.958 and 0.957, respectively. Furthermore, the interferences of the coexistence components can be eliminated with the aid of multivariate calibration. The method may provide a sensitive, effective and fast way for simultaneous quantitative analysis of phenol and p-nitrophenol in solution samples.