Infrared search and track (IRST) system is one of most important crucial system in modern war. With the military requirements on IRST and fast developing of infrared focal plane arrays (IRFPA), the third generation IRST system has been developed. The 3rd Gen IRST systems are characteristic of long detection and identification, 360° panoramic view coverage and single or dual band operation. In the paper, typical IRST systems are introduced including ARTEMIS IRST system, VAMPIR NG IRST system and Sea Spotter IRST system etc. IRST system will operate in multiple band and will be multiple functional. Here some new solutions such as using spherical sensor configuration and curved FPA which can improve performance of IRST system are also described.