Abstract: The difference of the development of modern micro-satellite from traditional large satellites is the introduction of the integration conception. The integrated design conception of the micro-satellite make the program reloading on-board form the trend in the development of small satellite. Based on the conception of modularization and standardization, a method for program reloading in the micro-satellite is proposed and discussed in detail to meet the requirement of the micro-satellite design principle in this paper. The discussion is based on the CCSDS telemetry and telecommand scheme and distributed system on board connected with CAN bus. Some extension of the CAN protocol is involved to distinguish the normal data and program data when the node is receiving bytes from the bus. And some additional processes ensure the program data's security and precision. This method can be developed for system bootloading or just for error handling and system re-construction on-board. It will have wide application in the future.