Abstract: In order to solve the problems of frequent downhole safety accidents, low early-warning efficiency, lagging safety monitoring technology in China, a downhole safety monitoring system with independent intellectual property rights was designed and developed. This system directly measures near-bit mechanical parameters and engineering parameters, and transmits the measured parameters to the drilling risk analysis and assessment module in real time by using the drilling fluid pulse, by which the received data can be analyzed and calculated to determine the type of drilling risk and assess the risk level. Field tests confirmed that the downhole safety system is fully functional and has a stable performance. The accuracy rate of the risk assessment is higher than 95%, and some technical indexes have reached the level of similar monitoring system abroad. The research show that the downhole safety monitoring system could reduce the drilling risk and drilling cost in deep complex formations. It could create great economic benefits for it has solved the problem of low early warning efficiency of downhole safety accidents.