The Programmable Logic Controller has the characteristics of strong anti-interference, high reliability, and simple programming, and is widely used in the field of industrial control. But, the traditional small programmable controller is difficult to embed the intelligent control algorithm into the control system. With the development of embedded microprocessors, programmable controllers use fast and more integrated microprocessors as CPUs to meet various needs in industry. This paper uses 32-bit embedded microprocessor STM32F407 as the control core and extended CAN bus as the fieldbus to design a programmable controller. The working principle of the system is described. The principle of interface circuit between each function module of PLC host and embedded microprocessor is discussed. FPGA is configured with digital I/O ports to expand the programmable controller I/O ports. An FPGA is applied to embed intelligent control algorithm. Because the embedded microprocessor with high integration degree is adopted in the system, the circuit design is simplified, and the reliability of the system is improved.