In order to solve the problem of ranging remote targets in IRST system, a method using triple-station IRST system is presented. Compared with the methods which use single-station of multiwave band IRST system and double-station either of single-wave band or multi-wave band IRST systems,this method possesses the merits of higher accuracy and more consistent in all azimuths. Simulation result shows that the IRST system can achieve a very high accuracy when the distance among the three stations is no less than 900 m. How to identify same targets among different stations in IRST system is also illustrated.