Abstract: Objective： To investigate the relationship between fluoride iontophoresis and remineralization of human root caries in vitro. Methods：Thirty-five human root samples were demineralized by acid-etching, randomly divided into five groups, then pretreated with 1.23%fluoride foam, 4%NaF solution with iontophoresis, 4%NaF solution simply and physiological saline with iontophoresis respectively. Then the samples were remineralized by pH-cycling, and the effects of remineralization were analyzed by laser scanning confocal microscope (LSCM) while lesions were photoed by scanning electronic microscope (SEM). Results：Observed by SEM, the two groups pretreated with 1.23%fluoride foam and 4%NaF solution with iontophoresis had smoother surfaces and they had significant differences in reducing demineralized depth and area compared with other groups (P <0.01)analyzed by LSCM, but there was no significant difference between themselves(P >0.05). Conclusions：Both fluoride iontophoresis and fluoride foam can promote remineralization of root caries, but have no significant differences in reducing demineralized depth and area.