A method used in a CAN micro controller for saving the power; the CAN micro controller comprises a core of the micro controller and a CAN/CAL module; the latter one comprises a plurality of sub modules; the sub modules processes the inputted CAN/CAL message with the work. The method comprises the following steps: the processor core is placed in the work of power (such as the work of sleep or idlemode); the CAN / CAL module work under the power; as well as the activation of CAN/CAL module to deal with the importation of CAL/CAN message (for example, multi-frame of sub-CAL/CAN message for automatic hardware assembly), thus putting an end to the work of its power-saving mode, and processor core power in their work. Implemented in the best case, by the CAN/CAL module will automatically enterthe multi-frame message sub-assembly, while the processor core is still work to maintain its power remains unchanged, the news of the multi-frame sub-assembly to reflect the completion, CAN/CAL having a complete disruption of the news, which referred to information in response to complete interruption of the end of the steps to implement. In another implementation example, the methods described in the following steps: the whole CAN microcontrollers, including the processor core and the CAN/CAL module, placed in the work of power-down mode; detection receiving input information; as well as detection activation of steps to respond to CAN/CAL module to handle the input message (for example, automatically on the multi-frame sub-CAL/CAN message do hardware assembly), thus the end of CAN / CAL module power-down work, but the processor core The power-down mode is not the end of the work.