Considering the importance of flood studies and methods for reducing flood damage in river engineering projects, flood flow behavior in rivers should be investigated. The Muskingum-Cunge method is a flood routing method, whose parameters are calculated based on the physical characteristics of the river.Selection of an appropriate reference discharge and the kinematic wave velocity is of utmost importance for calculating the routing parameters (X, K). In the present study, the accuracy of the Muskingum-Cunge method is studied by using the method in the river reach between the Mollasani hydrometric station in the upstream and Ahwaz hydrometric station in the downstream of the Karun River, Iran. The results show that if instead of using constant values for the parameters of the Muskingum-Cunge method, different parameters are used based onchanges in the flow depth, the accuracy of the Muskingum-Cunge method is increased, especially in the estimation of the hydrograph peak. In addition, taking into account the geometric characteristics of the river channel and flow conditions in the study river reach and the use of the Monoclinal wave relations to calculate the kinematic wave velocity increased the accuracy of the method. Accordingly, the Mean Relative Error (MRE) of total and flood peak section using the method presented in this study and the Monoclinal wave relations is equalto 2.78 and 3.37 percent, respectively. While by using constant values for the mentioned parameters and application of the conventional Muskingum-Cunge method, the error values are 6.18 and 13.70 percent, respectively.