Objective:More and more residual roots and residual crowns can be saved by root canal therapy and post-core crown and remain their function.The posterior residual roots and residual crowns are more usual than the anterior residual roots and residual crowns.Three-dimensional finite element model of maxillary first molar PFM restored by different number of fiber post with composite resin core were established by Micro-CT scan image combined with reverse engineering software.