Abstract: It is necessary to investigate the affecting mechanism between the trace water content and solidifying point of insulating oil and to take effective measures to monitor the insulating oil operating status, because the trace water impacts significantly on the solidifying point, pour point of insulating oil in some extent. Firstly,a series of oil samples were made up with different water content, and the experimental values of solidifying point and pour point of oil samples were tested. Then the mid-infrared spectral pictures of the oil samples were obtained, which can acquire the absorbance values of paraffin wax (at the wave number of 722 cm^-1), water (at the wave number of 1640,3 400,3 450,3 615 cm^-1). Finally, absorbance values of water and paraffin wax in characteristic wave number, the experimental data of solidifying point and pour point were combined to calculate the Pearson correlation coefficient and create linear correlation formula between these data and the water content. And according to the measured values of pouring point and solidifying point and infrared spectral absorbing values of oil samples at the wave number of 722,1 640,3 400,3 450,3 615 cm^-1, the multiple linear regression model was constructed. Analysis results show the goodness of fitting model is 0.987 3, 0.993 6 respectively, the error between calculated values and measured values of pouring point and solidifying point is from 0.033% to 0.350%. According to the model, the laws of trace water impact on the solidifying point, pour point of insulating oil were discovered. It is shown that solidifying point pour point values of the oil tend to increase slightly with the increase of moisture content in the oil/water dispersion system, the effect of moisture on absorbance value of paraffin wax is obvious; and the foundation about on-line monitoring of trace water in oil is established.