In this study, the aeronautical and aerospace standard rocket injector have been analyzed with different aerodynamic parameters in order to understand the performance of the injectors in different atmospheric conditions. These injectors are the primary device to inject the fuel form the manifold to the ignition chamber. It creates the requited pressure, mass flow rate and the flow velocity in order to generate atomization of the fuel molecule. This atomization of the micro fuel droplet create fuel spray angle, which indeed produce high fuel burn rate. The injector with improper design may cause, unburnt fuel molecule, which will turn to carbon deposit inside the mixture chamber and gets corroded. In this paper the author has investigated the injector flow rate with respect to the injector throat area. The fuel used in this cold flow test study is commercial kerosene. The result indicates that, as the pressure at the inlet increases, the spray cone angle, mass flow rate and flow velocity also increases gradually. This numerical analysis where performed for various injector throat area with respect to various pressure rate from 20-100 psi. The best injector with all aerodynamic properties have been selected. This research paper will be benefit for the researchers and aeronautical industries, which help them to study the different aerodynamic parameter change in various injector throat area.fuel burning time to reduce the unburnt fuel and the engine is hybrid with low cost. Nowadays injector with high accuracy sensor are inbuilt with the injector head, which controls the flow with the pilot valves. Technologies are developing as the need and the demand of the product increases.