The invention discloses a temperature sensor which comprises a CPU, a probe input end connected with the CPU, a signal output end connected with the probe input end, a voltage stabilizer connected with the signal output end, an audible and visual alarm drive circuit connected with the CPU, and an audible and visual alarm circuit connected with the audible and visual alarm drive circuit; and meanwhile, the temperature sensor is also provided with a fifth variable resistor connected with a pin 2 of the CPU, a third variable resistor connected with the voltage stabilizer, and a NAND-gate integrated circuit connected with the audible and visual alarm drive circuit, an alarm buzzer and a light-emitting diode. The temperature sensor can adjust the working voltages of the CPU and the probe conveniently, and can carry out audible and visual alarm.