Objective：To observe the clinical results of using Casein phosphopeptide-amorphic calcium phosphate（CPP-ACP） for preventing enamel demineralization in the fixed orthodontic process. Methods：Totally 60 volunteers who were undergoing fixed or－thodontics in this study were randomly divided into 3 groups，20 volunteers in each group. Group A was control group and received routine dental health care. Group B appended fluoride foam based on group A while receiving routine dental health care. Group C appended CPP-ACP based on group A. From the start of treatments，their occlusion pictures were taken per month，totally 13 times a year. The clinical test index was calculated to see whether new plaque or caries appeared on the tooth surfaces，meanwhile the enamel demineralization index（EDI） was calculated. The SPSS 18.0 pack program was used for statistical analysis. Rank sum test was used to determine the numerical variable data; categorical data were determined by using the chi-square test. Results：（1）From the change of enamel demineralization in 3 groups，the EDI was increasing as time went on（ ?字2A＝259.615，P＝0.000， ?字2B=190.416，P=0.000， ?字2C=207.512，P=0.000）；（2）There were statistical differences in EDI among three groups. EDI was higher in groups A，C than in group B，while there was no statistical significance between group A and group C. Conclusion：The EDI and enamel demineralization dam－age degree has a positive correlation with the time spent in fixed appliance. Fluoride foam treatment can reduce EDI in patients with orthodontics. CPP-ACP is the effective and safety way to prevent enamel demineralization among volunteers.