According to comprehensive analysis of river closure risk, a summary of two kinds of reasonable risk variables and models characteristic of high drop and high flow velocity in river closure project are presented. This paper also puts forward the specific methods and procedures to calculate river closure risk probability by means of the data surveyed in practice and stochastic simulation method with an illustrating case study made on the data surveyed in practice. The calculation results tentatively indicate the consistency of the two models and some rules of risk probability. Based on the case study and, evaluation and treatment of river closure risk are further analyzed. A suggestion of reasonable risk severity is given that lays a basic foundation for risk decision of river closure scheme.