Abstract: To improve the simulation precision and speed of long-distance pipelines, the simulation model of hydraulic transient flow in long-distance liquid pipelines was established based on the basic principle of MacCormack format and flow equation.Take one pipeline as an example, in which the transient flow caused by valve closing and flow increasing was simulated by the simulation algorithm and the characteristic method respectively.The processing method for different boundary conditions in MacCormack format and the influence of Courant constant on the simulation results were discussed.The results show that, the MacCormack format can be used to accurately simulate the transient flow process of long-distance pipelines and, after the characteristic method was used to solve the estimated layer boundary parameters, its oscillation amplitude and convergence rate are better than that obtained by the characteristic simulation method.Moreover, the boundary condition of MacCormack format processed by characteristic method is conducive to converge than by linear extrapolation method.The research results can provide reference for transient flow simulation of long-distance pipelines.