Direct acting pressure regulator is widely used for ensuring high uniformity and security for irrigation system. This research is aimed to investigate the effect of geometric and spring parameters of the pressure regulator on its regulating performance. For this purpose, an improved numerical simulation method was presented to obtain the entire characteristic curves including both the performance line of unregulated segment and performance curve of regulated segment. The modification of partial boundary conditions and calculating process of the dynamic model which was established in a previous study were carried out. The flow rate of pressure regulator calculation domain was controlled by a further downstream orifice along with the appropriate pipe length before and after the orifice, instead of directly setting the flow rate on the regulator outlet boundary. The cross section area of the orifice increased or decreased by its boundary moving till the desired flow rate obtained. The technique of layering dynamic mesh was employed for the movement of the orifice and the regulating plunger boundaries and mesh deformation of surrounding flow domain. The velocity of the orifice boundary, the calculation process of dynamic equilibrium of the regulating plunger, and the spring stiffness were carried out using a special user defined functions developed to couple with ANSYS Fluent code in every time step. Results of numerical simulations under inlet pressure ranging from 0.025 to 0.4 MPa and different flow rate conditions were verified by laboratory measurements. The influence of the geometric and spring parameters of the pressure regulator on its preset pressure and initial regulating pressure was investigated using the validated numerical simulation method by single-factor and five-level experiment design. The results shown that the relative deviation between numerical preset pressure and slope of performance line of unregulated segment and test values lay within -19.3 and 9.4 %, respectively. Numerically predicted performance indexes were in reasonable agreement with those obtained by experimental tests, which verified the reliability and calculation accuracy of the proposed numerical simulation method. The preset pressure dropped nonlinearly as the increase of two parameters affecting the force induced by water pressure difference of the regulating plunger which were the sectional areas of plunger upstream face and downstream face. The preset pressure rose proportionally with the increase of three parameters affecting the spring force that were the height of the flow orifice of the seat, the spring stiffness, and the pre-stressed spring length. The initial regulating pressure reduced with increase in the sectional area of plunger upstream face, the height of the flow orifice of the seat, the spring stiffness, and pre-stressed spring length respectively, whereas with a decrease in the sectional area of plunger downstream face. Effects of geometrical and spring parameters on regulating performance are successfully revealed thought the computational fluid dynamics analysis which forms the theoretical basis for future design and optimization of pressure regulator.%为提高压力调节器的设计效率、改善调压性能，该文基于直动式压力调节器物理机理模型，通过改进数值模型的边界条件和计算流程，模拟计算了不同结构和弹簧参数的压力调节器的完整调压特性曲线，分析并得到了结构参数和弹簧参数对预置压力和起调压力影响作用的规律。结果表明，预置压力与影响调节杆上下游压力差的参数，即调节杆上、下游断面面积之间为非线性负相关关系，与影响弹簧力的参数，即花篮进水口高度、弹簧刚度和预压缩长度之间为线性正相关关系；通过增大调节杆上游断面面积、花篮进水口高度、弹簧刚度和预压缩长度或减少调节杆下游断面面积可降低起调压力。结构参数和弹簧参数对调压性能的影响规律，可为各参数取值提供参考。该研究揭示了压力调节器结构设计的关键因素，对指导压力调节器的设计和性能优化具一定理论意义。
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