Abstract: To overcome the problem of the dust contamination in the measurement window of coal dust concentration sensor,based on the mechanism of dust separation by air curtain,the structure of the air sheath at the optical measure- ment window is put forward to improve the precision of the dust concentration measuring device. The velocity,pressure and the path of particle of the dust concentration at the pipe wall and the measurement port were obtained by simula- ting the gas-solid two-phase flow at the dust concentration path and the measurement port using the Fluent software, thus the structure of the sensor was optimized. Simulation and experimental results show that the velocity of air flow be- low 5 μm at the improved measurement port is higher than 1. 8 m / s,and the high velocity of air flow through the measurement channel effectively reduces the dust deposition below 5 μm,which ensures the accuracy and timeliness of the measurement.