OBJECTIVE To evaluate the remineralizing effect on artificial enamel subsurface lesions in vitro by 2% casein phosphopeptide-amorphous calcium fluoride phosphate complexes (CPP-ACFP) solution. METHODS Twenty-eight enamel blocks were cut from human third molars, in which 2 lesions were prepared from each block. The 28 samples were randomly assigned to the four study groups, in which each group was incubated in remineralization solution for 1, 3, 5, 10 days respectively. After remineralization the samples were sectioned, microradiographied and the mineral content were determined by microdensitometry. RESULTS The remineralizing solution replaced 9.19%, 14.27%, 29.07%, 38.45% of mineral lost after 1, 3, 5, 10 days respectively (y = 8.9316 x0.6347, R2 = 0.9322; y: remineralizing rate, x: time). Significant differences were found in remineralizing rate between any two groups using One-way Scheffe multiple comparison. CONCLUSIONS The 2% CPP-ACFP solution could significantly remineralize the artificial enamel subsurface lesion in vitro. The remineralizing rates were increased with the experiment time (within 10 days).