A series of insulating oil samples with different trace moisture contents were made up,and infrared spectrum scans were conducted on these samples to get the absorbance values of the water molecules at different characteristic wave numbers(namely 1 640 cm－1,3 400 cm－1,3 450 cm－1 and 3 615 cm－1).The uniformity coefficient of moisture in oil samples was defined,on the basis of which a calculation model for the kinematic viscosity of hydrous insulating oil was built up.The kinematic viscosity values of these oil samples under 40℃ were measured through experiments,which were compared with the calculated values based on the calculation model.The results showed that the calculation model can effectually reflect the influence rules of trace moisture on the kinematic viscosity of oil,and the correlation coefficient between the calculated values and the measured values was 0.9449,with an error range from －4.458×10－4 to 5.175×10－4.