Recently, smaller tolerance level of color shift owing to the geomagnetism is required in the development of high resolution of CRT. The color shift is cased by the electro beam trajectory. To reduce this beam trajectory, IMS is installed in CRT. But, to require of high resolution, IMS design is important. Conventionally, IMS design depended on mainly trial and error expermental method is at the edge of time and quality. Therefore, electromagnetic analysis taking account of degaussing process by FEM and beam trajectory analysis is developed and beam shift of product performance can be predicted before pre-production with this method. Besides this analysis and RSM(response surface methodology) , one of the optimization method, is applied to the preliminary design of IMS. IMS design to minimize beam shift is developed.