Abstract: Risk research on stability of the surrounding rock of the underground carven group is still in its initial period. In order to make a dynamic tracing of risk analysis of stability of the surrounding rock in the process of construction of the underground carven group rapidly and accurately, an evaluation system is composed of the observed data and patrol inspection data and numerical simulation data based on an analytic hierarchy process method and a fuzzy comprehensive evaluation method. Dynamic evaluation content and a dynamic criterion are also considered at the same time to determine the level of the probability of an accident of the surrounding rock of the underground carven group. The estimation methods of the loss which is suitable for the surrounding rock of the underground carven group are put forward based on different forms of destruction of the surrounding rock, and the concept of an equivalent law is also introduced to determine the level of the loss of the surrounding rock of the underground carven group if the accident happens. Finally, the risk level of the surrounding rock of the underground carven group is determined by risk matrix and both the level of probability of the accident of the surrounding rock of the underground carven group and the level of the loss of the surrounding rock of the underground carven group. A dynamic risk calculation system for stability of the surrounding rock of the underground carven group is developed by using microsoft visual C#. Net technology and SQL server 2008 database and Python language. The system is used to analyse risks in an underground carven group of a hydropower station project in China during its construction and it could find key factors acting on stability of the surrounding rock and accurately determing the danger zone of the surrounding rock. The progress of the construction of the underground carven group is real-time guided and the risk which may exist is also avoided so that the safety and reliability of construction of the underground cavern group can be ensured.