The model of plasmonic dichroic splitter in metal-insulator-metal (MIM) stucture with two subwavelength metallic slits is proposed in theory. The different visible lights passing through the double slits subwavelength structure produce optical splitting effects by filling with different insulators and setting the slit width, double slits width and thickness of the waveguide structure of double slit. The splitting effects are explained by using surface plasmon′ s principle and classical optics interference principle. Finite-difference time-domain (FDTD) method is adopted for numerical simulation. We simulate the light filed distribution in two cases of double slits with the same width filled in different insulators and the double slits with different width filled in same insulators. Both cases can achieve ideal splitting effects, and the biggest splitting ratio is 12. The MIM design has the advantage of simple structure, can be obtained by electron beam lithography system experiment equipment. Therefore, it has good application value.