The invention discloses a method for RBS analysis of a large-area target in a vacuum target chamber. According to the method, a two-dimensional mobile platform capable of performing horizontal and vertical movement relative to a beam current is arranged in the vacuum target chamber, movement of the two-dimensional mobile platform is controlled by using a control system, and the control system performs multi-point continuous measurement by using MAESTRO software, supports the OLE technology by using SIMNRA software, and implements SIMNRA batch analysis by using an EXCEL VBA script program. As the two-dimensional mobile platform capable of performing horizontal and vertical movement relative to the beam current is arranged in the vacuum target chamber, two-dimensional scanning of a target isrealized; compared with accelerator beam scanning, the method is easy to implement, and low in cost.