The risk evaluation of environmental monitoring indexes during deep excavation was systematically investigated and applied to a real project. The risk analysis was carried out based on the collected environmental monitoring data. The potential accidents which may be caused by the abnormal environmental monitoring indexes were analyzed. The risk sources which may arouse the value variation of the environmental monitoring indexes were disclosed. The dynamic controlling measurements for the risk sources were suggested. The successful application of the dynamic method to the real project further verified its feasibility.