Considering the engine tail flame of multi-tube rocket launch system ( MRLS) is too big, which causes inconven-ient for small space launching. In this paper, the tail flame forwardly exhausted by square launch tube is developed to solve thisproblem. According to the rocket launch requirements, the model of square launch tube is established. Gas of engine is diversed bythe deflector at the bottom of the square launch tube and exhausted through the channel between the circular orientator and the squarelaunch tube. The simulation analysis of internal flow field of launch tube provides a reference for improving MRLS.
