This paper summarizes material system and status of third-generation Infrared photodetector arrays,and then analyzes the trend of infrared photodetectors.Firstly,infrared photodetector and its three main stages are introduced briefly.It is followed by discussions the material system and their progress of third-generation infrared photodetector arrays with HgCdTe photodiodes,quantum-well photoconductors,type-Ⅱ strained-layer superlattices and quantum dot IR photodetectors.This paper also presents the new material choices and the trends of third-generation Infrared photodetector arrays.