Surface plasmon polaritons can localize the photons near the metal surface, forming a strong near-field energy density, which affects the efficiency of illumination for molecules and the coefficient of utilization for optical-voltage materials near the metal surface. We analyze the absorption spectrum for the metal-insulator hybrid structure grating and give out the surface plasmon coupling condition according to structure and filling factor. We prove that when filling factor is high enough to form a tiny gap between grating elements, the efficiency for photons to be coupled into surface plasmon polaritons can reach above 94%.