Abstract: The collapse of high and steep dangerous rock in the gorge area produces huge surge hazards, which seriously endangers the safety of waterways and scenic spots. However, the systematic research on the surge caused by perilous rock collapse is not enough, and the targeted rapid assessment technology needs to be strengthened. The purpose of this paper is to establish a calculation system of dangerous rock surge formula for different instability modes, so as to strengthen the rapid assessment technology of surge disaster caused by high and steep dangerous rock collapse in canyon area. The surge calculation formulas suitable for different instability modes of perilous rock mass are systematically sorted out, and the calculation system of the whole process formula of perilous rock mass surge suitable for different instability modes is established. Based on this system, the calculation engine of perilous rock surge is compiled. By using the formula method to calculate the surge of the typical crushed Longmenzhai dangerous rock mass, it is found that the maximum first wave height is 13.9 m at 175 m water level, the propagation wave height is 1.75 m at 2 km, and the climbing height at the wharf is 2.91m. The error with the numerical simulation results is within 20 %, which verifies the feasibility of the calculation system and analyzes the surge risk. Then, the calculation system is used to calculate the surge of the typical falling Yuxiakou dangerous rock mass and the typical toppling Brazilian Capitoliu dangerous rock mass. Both dangerous rock masses enter the low-risk area after 200 m surge propagation, which reflects the calculation system under different instability modes.