Hydraulic transmission has the advantages of simple structure, high transmission precision, bear high power, etc., widely used in engineering machinery, aerospace, automotive industry and other fields. However, there are problems such as difficult fault diagnosis, easy oil leakage, high maintenance cost, in order to monitor the real-time dynamics of the hydraulic system and the reliability of the operation, this paper proposes a hydraulic system design based on the digital twin system, and carries out a research around the real-time monitoring of the hydraulic digital twin system and the virtual reality synchronization. A hydraulic system digital twin framework is constructed, containing physical entity layer, virtual twin layer, twin data layer, information interaction layer and visualization application layer. The online operation of the hydraulic system twin is monitored jointly by sensing data and simulation data, and the real-time simulation of the digital twin realizes the visualization of the operation process of the hydraulic system, improves the reliability of the hydraulic system work, and provides a new research idea for the realization of the hydraulic system design based on the digital twin.