Abstract: In modern managed pressure drilling operation,automatic choke manifold is used to provide and control wellhead back pressure so as to control formation pressure.Due to the nonlinear relationship between regulating pressure and choke valve opening,it is difficult to adjust the choke valve accurately by a single choke valve within the scope of full opening in conventional choke manifold.In order to enhance controlling precision,the corresponding relation of pressure regulation performance and flow rate was established based on the three working states of choke valve,the model of pressure regulation performance was also developed.By analyzing the pressure adjusting precision and the effect of flow rate on pressure regulation performance,it is considered that pressure regulation performance of choke valve is somewhat non-linear,optimization of valve core can increase its effective working range,but it can’t eliminate super-adjusting scope,the flow rate of drilling fluids has a great effect on pressure regulation performance of choke valve,the flow rate should be paid great attention when designing the choke manifold.