The invention discloses a thermostat device for a nozzle of an injection molding machine and a warning system thereof, and belongs to the field of the injection molding machine. The thermostat devicecomprises a nozzle body of the injection molding machine. The upper end of the nozzle body of the injection molding machine is fixedly connected with a heat conducting plate and a thermostatic detection frame. The thermostatic detection frame is located on the outside of the heat conducting plate. The upper end of the heat conducting plate is fixedly connected with a glass reaction tube. The upperend of the glass reaction tube is provided with a pre-blasting mechanism. The pre-blasting mechanism comprises an air bag inlet pipe and a pre-blasting air bag. The information of the color change inthe glass reaction tube can be received through a color sensor, and an optical fiber sensor receives the change of laser beam intensity, so that the effect of the temperature change at the nozzle ofthe injection molding machine is judged. When the temperature exceeds the required temperature range, an alarm is given to remind the staff in time to control the temperature of the nozzle of the injection molding machine. At the same time, the accuracy of the information is increased and the contingency of the data is reduced through the double detection of the temperature.