For the change of injection consistency led by structural parameter changing during the use of injector, the vulnerable structure of injector was obtained based on CRIN series injector according to the analysis of hydrodynamic and mechanical motion, and the simulation model of injector was further built by using the AMESim software. With the BoxBehnken design method, the regression equation between test factors and test indexes were established and the influence of test factor on test index was analyzed based on test factors of gap between needle valve parts, clearance between plunger matching parts, needle valve lift and armature lift and test indexes of fuel injection variation and response time variation. According to the results of multi-objective optimization, when the clearance between plunger matching parts, gap between needle valve parts, armature lift and needle valve lift was 4.38 μm, 2.66 μm, 0.05 mm and 0.34 mm respectively, the change rate of 1.70% and 2.27% for fuel injection and response time respectively was achieved, therefore the optimal injection consistency was realized. Finally, it was thought that the change rate of fuel injection and response time could meet the requirements of national standards and engineering requirements for fuel injection consistency when the above mentioned four parameters were 3.05-5.93 μm, 1.50-3.95 μm, 0.045-0.053 mm and 0.33-0.38 mm respectively after combining with the results of numerical calculation.