The geometric model of internal runner was constructed in Pro/E software.The internal flow field of the Rain Bird 30PSH impact sprinkler was conducted by using computational fluid dynamics (CFD) software Fluent with RNG k—εmodel at ten different pressure values and four types of range nozzle. Relationship between flow rate, inlet pressure and average velocity of outlet of range and spreader nozzle were evaluated. The results showed the flow rate of spreader nozzle was almost the same regardless of shifting the diameter of range nozzle. The distribution between range and spreader nozzle depended on the diameter of range nozzle was independent with inlet pressure. The average velocity magnitude of the range nozzle increased with the increasing of inlet pressure but spreader nozzle would not. The turbulent kinetic energy of range and spreader increased with the increasing of inlet pressure was independent with nozzle size. The standard deviation of static pressure, turbulent kinetic energy, velocity of range nozzle and static pressure of spreader nozzle were almost in direct proportion to inlet pressure. Biggish and irregular changing was happened to standard deviation of turbulent kinetic energy and velocity of spreader nozzle. Flow field visualization indicated that joint of runner and spreader nozzle had maximal static pressure. 