The invention provides a junction sensing device for a power supply. A wireless temperature sensor is in network connection with a handheld acquisition device, and temperature information acquired by the handheld acquisition device is transmitted to a monitoring computer through a data transmission base station. The wireless temperature sensor and the handheld acquisition device form a temperature detection device, and the temperature information is transmitted to the monitoring computer through the data transmission base station, so that the temperature state of power equipment can be timely and effectively detected, system recording and monitoring are performed through a network, the problem is timely solved, and an accident caused by overhigh temperature of transmission equipment is prevented; and the device is suitable to be used as a junction temperature monitoring device for the transmission equipment and the power equipment.