Abstract: The dose controller is an integral unit of the active heavy ion beam scanning system. The interaction between beam radiation position and dose is achieved through its conjunction with the position controller. Therefore it can strictly control beam to scan point by point in three-dimensional space and assure each point radiation dose in the prescription dose. The controller used FPGA technology, and the functions of dose control and SDRAM control were achieved on ACEX1K50 chip. The principle of dose control and the modules specific implementation process were described. It has broad prospects for use on the further expanding heavy ion therapy.