In this study, 3-D model of Urea injector nozzle is generated by applying Reverse-engineering technique, and internal flow characteristics were analyzed using CFD with moving grid technique. Injected mass flow rates of D type injector is twice that of H type injector. It is believed that the difference of the mass flow rate is caused by the difference of the engine displacement. For both injectors, the maximum mass flow rate occurs at the moment that the needle acceleration reaches its maximum valve. H type injector shows relatively stable mass flow rate characteristics, and H type injector is recommended to control injection rate accurately.