A mine environmental monitoring system which is composed of hardware and user software is developed. The functions of the hardware are monitoring the complex coal mine environmental factors, uploading monitoring data and controlling the designed environmental equipment. The user software is programmed by Java and it stores the uploaded data in a database, draws curves, makes predictions and so on. Through analyzing and processing the uploaded data, the user software can makes decisions and sends control commands to the hardware, thus the designed environmental equipments change the environment. Additionally, an improved multi-sensor information fusion algorithm is proposed to improve the stability and accuracy of this system. Finally, an experiment is carried out to test our system.