The ion beam figuring is a kind of advanced technology of mirror processing. It has the advantages of high processing precision, high speed and no damage to the mirror surface. The ion beam figuring machine is established by using a one meter diameter vacuum coating plant in this research project. Mechanical scanning device, ion source and workpiece make up of the machine. Water, electricity and gas will be imported to the vacuum chamber. The computer software, extracting the error function between the ion beam processing function and mirror surface function by using the data of interferometer measuring, will calculate the dwell-time function in the course of processing. The computer will control the whole process based on the dwell-time function. The experiment processing indicates that PV will reach 1/14λ and RMS will reach 1/70λ by once ion beam figuring.