Configuration standard solution in the concentration range of 1~25 mg·L-1 of potassium hydrogen phthalate was usded as experimental subject, Ultraviolet absorption spectra was collected, the COD quantitative analysis model was established by partial least squares with different pretreatment methods and the turbidity of the compensation effect analysis was given. The results show the model uses smoothing first derivative pretreatment method, internal cross validation RMSECV root mean square value of 0.122 27, principal component number 4, the square of the prediction model correlation coefficient is 0.999 8, and the relative prediction error is in the range of 0.03%~1.7%; for 0~100 NTU’s turbidity solution, the relative standard deviation RSD is 2.3% after compensation; with pH in the range of 3~10, influence can be ignored.