Along with the situation that the functions of smart meter become more and more complicated and more and more flexible, there exposed more and more software defects. Due to these questions, a design of smart meter software based on embedded RTOS is proposed. Through this design, the whole meter software is divided into kernel module, metering module, main application module and extensional application module. Fully using the properties of embedded RTOS in multitasking and inter-task communications, the whole software system is divided reasonably and orderly into several parts based on module and hierarchy design method. With this design method, it not only guarantees the stability and reliability of kernel functions, but also satisfies the flexibility of expanding new software functions.