BACKGROUND:: The durability and efficacy of casein phosphopeptide-stabilized amorphous calcium phosphate solution (CPP-ACP) on remineralization of enamel lesions are greater than calcium phosphate-based solution. However, the majority of studies focus on demineralization at enamel surface. OBJECTIVE:: To investigate the efficacy of CPP-ACP on remineralization of different surface of enamel etched. DESIGN, TIME AND SETTING:: A randomized control experiment was performed in Stomatology Hospital, Lanzhou University from May to July 2008. MATERIALS:: A total of 20 first premolar in maxillary extracted for orthodontic reasons were collected in Stomatology Hospital, Lanzhou University. METHODS:: The samples were randomly divided into two groups with 10 teeth in each group. Buccal and palatal surface of teeth were separately etched by 35% or 20% phosphoric acid gel in 20% for 60 seconds. Teeth were cut vertically along mesto-distal surface, the half etched of teeth were placed in the CPP-ACP solution to be remineralized for 10 days, and the other half were placed in deionized water as controls. Morphology of teeth was compared. MAIN OUTCOME MEASURES:: Morphological changes of teeth etched and re-mineralized in the CPP-ACP solution were observed by scanning electron microscopy (SEM). RESULTS:: SEM observation indicated that enamel surface became different fish scaled structures when they were etched by 35% and 20% phosphoric acid gel. On the surface of the enamel treated with phosphoric acid gel, a large amount of minerals deposited after remineralization in the CPP-ACP solution. The minerals were exiguous and the aggradation was uneven. There was not significant difference between the two structures. CONCLUSION:: CPP-ACP can promote remineralization on the surface of teeth enamel, and the extent of mineralization has no relation to the morphology of teeth enamel.