## 1 Introduction  
Safety is the top priority of coal mine production and plays an important role in it. In recent years, China has gained great achievements in the field of coal mine production safety, but the situation is still severe. In China, coal mining is mainly carried out underground, where the geological conditions are complicated [1; 2; 3]. Along with coal mining at greater depths, the amount of gas emission increases, and thus the risk of coal and gas outbursts grows. Besides, there are other natural factors that can cause disasters in underground mines, such as rock bursts, coal dust explosions and water leaks. With the addition of narrow working space, poor lighting, and many hidden dangers in each coal mining procedure, heavy casualties may occur for slight carelessness. Hence, the hazardous natural conditions and the adverse working conditions make underground coal mines full of numerous risk sources and hidden dangers. The focus of coal mine production safety is to strengthen monitoring and early warning of possible natural disasters such as gas, fires, pressure, coal dust and floods, since monitoring and controlling, predicting and warning are the precondition and guarantee for the \"safety first, prevention crucial\" policy, and the key to prevent accidents. As an important guarantee for coal mine safety production, the Cable Monitoring System (CMS) technology has gone very far, and theoretical problems and the key technology issues involved have been resolved already [1]. Due to the complex working conditions in underground coal mines and the limitations of the CMS, it is difficult for the CMS itself to comprehensively and effectively monitor the environmental parameters which have important impact on the coal mine safety production, such as gas, pressure, coal dust, temperature, wind speed and carbon monoxide (CO) levels. Moreover, the area that is difficult to monitor for the CMS, is generally where the hidden dangers are most prominent, so plenty of hidden dangers are left inevitably, which is a difficult situation for the traditional CMS to overcome. Whereas, by using wireless methods, a wireless monitoring system can effectively, instantly and flexibly monitor the areas that are difficult to monitor for the CMS. Wireless Sensor Networks (WSNs) are a new kind of _ad hoc_ network, which consist of hundreds to thousands of WSN nodes that communicate with each other, and can monitor areas from small to huge [2; 4]. In recent years, with the rapid development of mobile communication and high-speed electronic devices, sensors with characteristics of low power consumption, programmability, multi-parameter sensing and wireless communication ability have been put into practical use. With outstanding advantages of ease of configuration, flexibility to shrink or expand the monitoring range, strong fault-tolerance and mobility, WSNs can play an important role in monitoring and analyzing dynamic, hostile and unfamiliar environments. Therefore, based on the WSN technology, a kind of mesh WSN with multi-parameter monitoring for underground coal mines was established, acting as a supplement to the CMS. Since the WSN nodes have multiple interfaces to connect different kinds of sensors, multiple types of environmental parameters can be monitored. Using WSNs to monitor the environment of coal mines is not a new topic [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. WSN technologies for this application have been investigated before. For instance, strategies for deploying a long distance WSN in an underground coal mine have been put forwarded by [PERSON] [7], [PERSON] has discussed the challenges of using WSNs in underground environments in his theoretical research [12], and [PERSON] has proposed a multi-path WSN routing protocol for mine security monitoring [14]. Most of these works are theoretical research focusing on certain technology or just focusing on the technologies of the WSN. In this paper, with the aim of practical use, an integrated monitoring system including the WSN and the CMS is constructed.