Research conclusions : The discrimination should be done and the countermeasures should be worked out in the courses of design, construction and management of karst tunnel for avoiding the risk. In the design period, the classification of risk degree should be made for karst tunnel and with it the relative design should be made. In the construction period, the training should be reinforced for security and the relative construction principle and method, risk discrimination and fleeing system should be implemented and provided in the whole course of construction. For those complicated karat tunnels, the prediction and forecast should be done in advance with special management and the treatment of karst should be done based on pragram and system with management of the special fund.