Among the potential accidents that can lead to fatal injuries in underground coal mines, gas explosion accidents have been recognized as the leading threat to miners' safety in China. Moreover, such accidents are triggered predominantly by human-related hazards, namely, the unsafe behaviours of humans. In underground coal mines, there are a considerable number of unsafe behaviours that can trigger gas explosion accidents. Consequently, how to determine scientifically the risk management priority of human unsafe behaviour is the basis of pre-controlling gas explosion accidents effectively. Therefore, the method of assessing the risk value of unsafe behaviour is proposed based on the analysis of its characteristics, and then a risk assessment model is constructed. Under this framework, the risk assessment model is composed of probability, importance degree, and loss, and the risk value is the product of the three. Furthermore, the probability and importance degree can be obtained by assessing the degree of unreliability of unsafe behaviour and analysing the degree of influence in the fault tree using the Boolean algebra algorithm, respectively. Finally, according to the risk values, the priority for controlling unsafe behaviours can be obtained to provide a theoretical basis for the effective control of gas explosion accidents.