Based on the local resistance computation model for a choke valve and using the flow characteristics of choke valves, we studied the relationships between the back pressure of a parallel choke assembly and the opening extent of choke valves and developed a model to characterize the pressure regime of the manifold assembly. A comparison of pressure characteristic curves shows that a parallel choke manifold assembly has obvious advantages over the conventional serial type including high linearity of pressure-regulating characteristics curves, the elimination of the overshoot interval, wider effective regulating interval and the higher system security. Laboratory hydraulic experiments have validated the capability of a back pressure control model for the parallel choke assembly to accurately control pressure. This study is of great theoretical and practical significance to further improve the performance of chokes used in managed pressure well drilling.