By using rigorous coupled-wave analysis method, the process tolerance of broadband polarization independent reflector with multi-subpart profile resonant grating is investigated. The theoretical analysis shows that, in the wavelength range of 1.62-1.76 μm, the change of 20 nm of critical structural parameters such as period and thickness, modulation profile, middle layer thickness, buffer thickness of micro-nano resonant grating has a negligible effect on the reflectance spectrum of the device. The results show that the proposed reflector has good processing tolerance in the existing processing error range, which is conducive to the processing and fabrication of the device.