A novel integrated resonant-cavity-frequency-selectivity inclined-mirror coupling encapsulated-core wave-guide(RICE WG) photodetector(PDs) was described.Detailed design processes and numerical simulations were investigated theoretically.The novel structure makes device quantum efficiency decouple with the response bandwidth and spectrum linewidth simultaneously.Through performance simulation and optimization,the results indicate that the tradeoff between spectral response linewidth and quantum efficiency no longer exist.the PIN of RICE WG can achieve spectral response linewidth <1 nm and quantum efficiency >80% simultaneously.Additionally,we discussed the approach to realize it.