The dynamic characteristics of pump response to transient events were investigated by combining the Method of Characteristic (MOC) and Computational Fluid Dynamics (CFD) together. In a typical pump–pipeline–valve system, similar to the reactor system, the pump is treated as three-dimensional CFD model using Fluent code, whereas the rest is represented by one-dimensional components using MOC code. Meanwhile, a description of the coupling theory and procedure ensuring proper communication within the two codes is given. Then the pump transient characteristics caused by downstream valve closing and opening were analyzed and compared with the steady characteristic to study the effect of fluid inertia on the pump transient performance. It was found that the H-Q curve in transient operation evidently deviates from the steady-state value and shows two distinct patterns of deviation, and the cause of the deviation was further explained by the comparison of pump internal and external characteristics. All the results showed that MOC–CFD is an efficient and promising way for simulating the interaction between pump model and piping system.