Abstract: An optical limiter has been designed based on the step ring grating. The intensity distribution of a beam transmitting through the limiter was derived theoretically and simulated, and the changes rules of intensity distribution with grating indexes were analyzed in numerical methods. The simulation results show that this grating is a kind of blazed grating, and the incident energy would mainly distribute on one or two wide light rings apart from the aperture center for the limiter with suitable indexes. The light ring position is determined by grating depth step and period. It changes in period when the depth step increases, and the lightest ring position is independent of incident wavelengths if suitable indexes are selected, which is useful for designing effective multiband limiters.