Abstract: A method for controlling the load of a transformer based on a hot spot temperature measured by using the fiber grating technology. In the production process of a transformer, fiber grating sensors are arranged on the upper portion of an internal winding of the transformer, at the position of a leading wire and on the upper portion of an iron core, and the control of a cooler of the transformer is directed by using real-time temperature data measured by the fiber grating sensors. In this method, the fiber grating sensors are used to monitor the internal hottest spot temperature of the transformer to conduct the cooling control of the transformer, so that the control of a cooling system of the transformer can be conducted effectively in accordance with the operation state of the transformer itself and the influence of the external environment.