The objective of the new method is to develop an innovative multicomponent moulding with one die, which is specially applicable in automobile industry. The new concept multi component moulding system of this research is the secondary cavity for secondary material which is formed by the moving of the core. Recently, this method has faced with problem of flash, short shot in filling and also gluing when manufacturing multi component of car door-trim with electrical core-back coinjection machine.Process parameters, material and injection die which consist lots of parameters such as injection pressure, ram speed, mold-melt temperature, core back distance, viscosity of material and so on are considered to solve problem of new technique. The methodology combines the use of the design of experiment (DOE) and CAE flow simulation software, to reduce the injection molding parameters and to predict the role of parameters on process of manufacturing. We simulate the process with models of the three-dimensional geometry of the multicomponent moulding, which have a minimum distance of core back of 1.5 mm(second component), and study the variation of different process parameters as this core back increased. From the CAE analysis, the optimum process parameters are obtained with the optimal distance of core back of 2.0 mm. Successive processes for moulding car door-trim multi component in practical experiments explain for the good accuracy of the methodology and the efficiency of the proposed optimization parameters.