The invention discloses a programmable double fieldbus conversion interface and a method. An NCUC and Profibus-DP fieldbus conversion interface device is supported. Meanwhile, connected serial port communication equipment or internet access communication equipment can be in reliable communication with equipment supporting the NCUC or Profibus-DP fieldbus through the interface conversion device, and heterogeneous network interconnection is achieved. An STM32F103RET6 microcontroller is adopted and is a 32-bit high-performance microcontroller, a specialized Profibus-DP protocol chip is adopted, communication between user data and the Profibus-DP bus is achieved, and the processing speed is higher. The function of connecting the serial port equipment and the internet access equipment into the NCUC fieldbus and the Profibus-DP fieldbus for communication is achieved. The advantages of being high in processing speed, high in flexibility, reliable in communication and the like are achieved, the design complexity of an industrial field NCUC and Profibus-DP slave station can be reduced, the technical threshold of using the NCUC and the Profibus-DP for a user can be lowered, the development cost can be reduced, and product integration and fast product development are promoted.