Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) technology combined with the partial least squares (PLS) regression were successfully applied for the rapid no-reagent determination of chemical oxygen demand (COD) for sugar refinery wastewater. Among 105 samples, 45 samples were randomly selected as the validation set. The remaining 60 samples were divided into the calibration set (40 samples) and the prediction set (20 samples) for a total of 30 times with certain similarities. The appropriate model with stability was established on the waveband of 4500 cm-1 to 600 cm-1. The optimal PLS factor was 4, the modeling effect M-SEPAve, M-RP,Ave, M-SEPStd, and M-RP,Std were 38.1 mg/L, 0.944, 3.2 mg/L, and 0.013, respectively, the validation effect V-SEP and V-RP were 38.2 mg/L and 0.949, respectively, which has good prediction effect and stability. The results provide a reliable analytical model for the monitoring of COD in sugar refinery wastewater.