Aiming at the two distinct phenomena appeared in the EC-5 sensor temperature experiment, a theoretical model on variation of soil moisture content with temperature was established according to the influence of temperature on soil permittivity and electrical conductivity. The simulation based on the model shows that the variation tendency of soil moisture content with temperature measured by the EC-5 sensor is closely related to the soil electrical conductivity. Using least squares support vector machine, the sensor temperature compensation function was built and corresponding compensation algorithm was proposed. The results of the experiment indicate that the sensor measurement errors caused by temperature are effectively offset.