Objective To confirm if denuded bone on lateral aspects of the hard palate of surgical repairs of the cleft palate is the main reason of causing disturbance of facial growth and to investigate the mechanism.Methods 48 SD ratswere employed in the study. Among them 40 animalswere divided into normal control and experimental group randomly. Normal controlwas not op- erated. Hard palate mucoperiosteum on the left side in experimental group were excised. Left hard palate mucoperiosteum in an- other 8 female three-week-old SD ratswere excisedwith same method andwere sacrificed at 2nd, 5th, 8th, and 12th day, respec- tively. The 8 rats were used for histological research.Results The width of all left sides hard palates in experimental group was significantly narrower than right side, and demonstrated statistical difference. Chronic osteomyelitis on the denuded hard palatewas observed.Conclusion The denuded bone wound might be a principal factor for the following maxillary growth deformity in cleft palate patients who received palatoplasty in childhood. The mechanism of causing the deformity might be wound and scar contrac- tion, decreased blood flow and nutrition plus chronic osteomyelitis.