A mountain disaster chain always brings about potential danger to the safety of people and the environment based on its characteristics of long time-scale, great destructive power, and broad scope. Mechanisms responsible for this hazard are represented by studying a landslide-caused disaster chain that occurred in the bank of Jinshajiang River, China on 10 October 2018. The evolution process of this disaster chain is simulated and analyzed using a coupled model that consists of several depth-averaged equations, and the results agree well with the measured data. Furthermore, several factors, including frictional coefficient, inflow flux, and critical dam slope coefficient, are tested by applying different values. Results indicate that the evolution of a mountain disaster chain can change at each stage with different initial conditions.