The invention uses infrared ray to measure the use distance of electric tool, comprising at least one MCU(microprocessor), ADC(analog to digital converter)interface of MCU, respectively connecting with filter capacitor, a third resistance, wherein another end of the filter capacitor is connected with ground and another end of third resistance is connected with a infrared receiving tube, and another end of the infrared receiving tube is connected with the fourth resistance; PWM(pulse width modulation) interface of MCU connected with triode base, the triode base connected with the first resistance, triode collector connected with a infrared transmitting tube; MCU- common I/O interface connected with a second resistance, wherein another end of the second resistance is connected with an indicator light.