We demonstrate in the paper that user movement has great influences on the system performance of mobile cellular networks. We also develop a system model to study to what extent the influences will be, with focusing on the user movement simulation. We concern the parameters that determine the system performance of mobile cellular networks. We show partially in this paper that these parameters vary while user movement changes, but the effects are interactive. Since handoff calls are given a higher priority over new calls and GC mechanism is employed, our analysis shows that a mature mobile cellular network should make use of user movement characteristics and dynamically adjust its reservation threshold of the handoff call requests. Extensive simulation results validate our analysis.