Aiming at the problems of low intelligence, weak remote operation ability, and low maintenance accuracy of overlay welding in the space of the narrow pipe, the requirements of the virtual monitoring system of maintenance welding robot in the vertical pipe driven by twin data was analyzed, and the overall design scheme of “twin data-driven, virtual reality presentation” was proposed, and a digital twin model of maintenance welding robot in the marine riser was built. Aiming at the problem of twin data interaction, a twin data communication system was established based on ADS(automation device specification) communication technology. The Unity3D software was used to develop a virtual reality monitoring system for maintenance welding robots in risers. The experimental results show that the virtual monitoring system of the overlay welding process runs stably, the dynamic adjustment process is smooth, the overlay welding lap rate is reasonable, and the overlay welding bead is smooth, which greatly reduces the work intensity of the operator and provides technical support for the digital and intelligent overlay welding maintenance robot system.