Abstract: In the embedded system of no hardware support, such as memory management unit (MMU), software is usually taken as a whole in the system, in practice, because the changes of hardware device or application function could lead to the overall replacement of software, the software testing, verification, replacement complex, and increased cost. The article analyzed the independence principle of application software and hardware based on several typical systems, combined with the ARM Cortex-M series processors, presented the method to implement the independence of application software and hardware in embedded system of no memory management unit(MMU). This method is suitable to construct more flexible embedded system, and reduce the cost and difficulty of system upgrade.