Abstract: A tandem cold rolling simulation system with 4-level architecture was developed for the 4-high 5-stand mill system for 2030 mm sheet in a steel plant. The structure and functions of the virtual object are introduced to give a description of the dynamics of rolling process and physical device. A distributed database system (DDP3S) was developed for the virtual object, and the modularization design of the simulation software improved its security and maintainability. The application, client and resource hierarchies of the virtual object which the Web-based simulation platform comprises are thus implemented and presented. This virtual object of tandem cold rolling simulation system provides an appropriate platform for virtual rolling experiments to improve rolling automation technique.