Modern large-scale mechanical equipment usually has diverse tasks and complex structures. The traditional development and design, task management and operation and maintenance modes are increasingly difficult to meet the practical needs. With the development of computer and information technology, digital twin technology has been proposed and widely concerned. It can realize the interaction and fusion between an object's physical entity and virtual model by establishing a model with multi-physics, multi-scale, multi-level and multi-disciplinary attributes. It has the characteristics of virtual-real synchronization, faithful mapping, and high fidelity, which provides a new way to solve the above problems. Therefore, based on the basic theory and technology of digital twin, taking typical complex equipment as the research object, this paper proposes the overall architecture of digital equipment, summarizes the key technologies of developing digital equipment, and explores several potential application services based on digital twin, such as product design, auxiliary decision-making, intelligent maintenance and health management, to provide theoretical and methodological references for further research and equipment application in the future.