Abstract: In order to improve quality of underground wireless communication and ensure effective communication, influence of underground coal dust concentration and humidity on electromagnetic wave transmission was researched. Calculation formula of electromagnetic waves absorption of coal dust and water vapor were given through theoretical analysis, and it was concluded that coal dust absorption effect was the main factor affecting underground wireless communication capability. Electromagnetic losses at different coal dust concentrations, humidity and frequency were analyzed by simulation, and it was concluded that coal dust concentration had obvious influence on electromagnetic wave transmission, and the influence of humidity on electromagnetic wave attenuation was obviously less than that of coal dust. On this basis, data transmission performance of point—to—point wireless communication module was tested in underground roadway for different distances, different coal dust concentrations and different humidity environments. The test results show that within 50 m, all communication test results are stable and there is no packet loss; when distance reaches 100 m and the coal dust concentration exceeds 60 mg/m3, packet loss phenomenon begins to occur, and as coal dust concentration increases, the package lost phenomenon intensifies; humidity change has no effect on packet loss, but data transmission accuracy rate decreases when the humidity is high.