Abstract: For problem that existing dust measurement methods can not real-timely reflect dust concentration of on-site air, the paper designed a mine-used dust concentration sensor, described composition, working principle of the sensor and its application in automatic spraying device for dust falling in coal mine. The sensor uses principle of laser light scattering to measure concentration of dust particles suspended in air, adopts precision mechanical structure and laser lens brush mirror institutions designed by dust sedimentation principle to ensure measurements reliability and accuracy of the sensor.