Abstract: Based on the Product,Process and Resources （PPR） technology,the establishing technology of virtual maintenance environment for the reactor system and the process structure tree for virtual maintenance is studied,and the flow for the maintainability design and simulation for reactor system is put forward.Based on the subsection simulation of maintenance process and layered design of maintenance actions,the leveled structure of the reactor system virtual maintenance task is studied.The relation for the data of product,process and resource is described by Plan Evaluation and Review Technology （PERT） diagram to define the maintenance operation.