The photonic crystal can be employed as the antireflection coating due to its photon-trapping ability,and such photonic crystal structure can reduce the dark current,so it is widely investigated in the field of infrared detectors.The simulation and design process on HgCdTe medium-wave infrared detector with photon-trapping structure are demonstrated.With the help of FDTD based model,the quantum efficiency has risen by nearly 20% by optimizing the photonic crystal structure.