In liquid propellant engines, the propellants (fuel and oxidizer) after passing the injectors, are injected to combustion chamber. Generally, in liquid propellant engines, two types of injectors - direct flow and centrifugal flow - are used. The direct flow injector, actuates as an orifice. The input flow to a centrifugal injector, gets the angular momentum and goes out conically. The angular momentum causes the powdering of output fluid. The injecting cones collide to each other and the mixing operation is accomplished. The mixing and powdering of droplets in the centrifugal injectors are accomplished better than the direct flow injectors. To this reason, in modern liquid propellant engines, the centrifugal injectors are used. The centrifugal injectors are divided to two types : one component and two components. At one component injectors, the fuel and oxidizer are injected separately, but at two components injectors, both oxidizer and fuel are injected from a complex structure. The injection rate at injector plate, is one of the effective parameters on walls cooling, combustion stability and propulsive force (thrust) in the combustion chamber. In order to attaining the suitable injection rate, the effect of injector arrangement must be investigated. In this paper, after designing five different plans, the optimum injection rate has been investigated and selected. The method is the meshing of injector plate, determining the input value of oxidizer and fuel rates into each element and then computation of injection rate by means of a computer code. The mentioned code computes the distribution of flow rate at the lateral section of combustion chamber by using the geometric conditions of injector plate, the position and the flow rate of injectors. This code is usable for all kinds of one and two components injectors and has been validated by using of experimental test possilbilities and the error has been lower than six percent.