A large ion beam figuring plant which can process up to 1.5m mirror in diameter has been developed. The plant adopts five axes scanning mode. The mirror with which the five axes scanning system is set face to face is placed vertically when working that can reduce the adverse effect of the flour dust to the mirror and the ion source. The mirror and the five axes scanning system are installed on two doors respectively. The open-close type of the door is a hanging bridge type. And the door will be horizontal when completely opening that will be convenient for installing the mirror and maintaining the system. Two software which are used for calculating the dwell-time and controlling the five axes system are programmed. The five axes system will always keep normal direction following when working.