This paper proposes a Resonant Cavity Enhance (RCE) photodetector (PD) b ased on a novel non-periodic high-contrast subwavelength grating (HCSG).The device is made of a top grating type It consists of upper reflector,PIN light detection structure and distributed Bragg reflector (DBR) lower reflector. The upper mirror is composed of a new type of non-periodic HCSG,which is composed of an Al₂O_3spacer layer formed afte r partial wet oxidation and an aperiodic GaAs grating.It achieves high reflection and convergence characteristics of TM mode polarized light in the 850nm band, and the reflectivity reaches 86.5% and Beam convergence is achieved at a focal l ength of 1.5μm.The lower mirror is composed of a GaAs periodic grating and GaAs/Al0.9Ga0.1As DBR.The Ga As periodic grating has a polarization selective characteristic for incident light,the polarized light transmittance for TM mode is 96.1%,and the polarized light transmittance for TE mode is only 3.7%.The device uses the transfer matrix theo ry method to simulate its quantum efficiency,and the quantum efficiency reaches 71.8%;the Poisson equation and t he carrier transport equation theoretical method are used to simulate the response bandwidth of the device,the full width at half maximum is close to 0.1nm.It effectively solves the problem that the high quantum efficiency and high respons e bandwidth of photodetectors are mutually restricted,and provides a good foundation for the development of next-generati on optical communication systems.