Abstract This paper briefly describes the characteristics of DCS, PLC and fieldbus systems, and discusses that DCS will eventually be replaced by fieldbus. Keywords Distributed control system Programmable controller Fieldbus control system 0. Introduction DCS, or Distributed Control System, is a new type of digital control system developed in the mid-1970s. It is a product of the combination of 4C technology, namely computer technology, control technology, communication technology and graphic display (CRT) technology. With the development of technology, it has also combined information (correspondence) management technology. The current DCS is a modern device for completing process control and information management (i.e. 5C technology) [1]. This system has been widely used in process control in various industries, especially in thermal power plants, and has achieved significant economic and social benefits. The development of DCS system represents the development direction and level of the field of automation control. 1. New Features of DCS Systems 1.1 The foundation of traditional DCS systems mainly consists of three elements: a. Network: A computer network is a network of interconnected computer systems connected through communication lines; b. Microprocessor: This is the hardware foundation of DCS; c. Graphics technology: The widespread application of DCS systems is due to the replacement of traditional analog screens with intuitive graphics technology. (Full text available for download: Application and Development of DCS, PLC, and Fieldbus Systems in Power Plants )