Micro intelligent programmable logic controller（PLC） has been widely used in various control system of electric power system. However the current micro intelligent PLC still adopts eight bites or sixteen bites single-chip microcomputer as its processor. To overcome its deficiency， an ARM embedded processor-based micro intelligent PLC is designed. The system framework is present concisely. The hardware design based on AT91SAM9260 chip and the software design with the embedded real-time operating system VxWorks， are introduced in detail.