Abstract: Objective To explore the effects of the highest oxidized folate (folic acid, FA) and reduced active folate (5-methyltetrahydrofolate, 5-MeTHF) on the methylations of LINE-1 and Alu, which were able to serve as surrogate markers for global genomic DNA methylation. Methods Human lymphoblast cell line GM12593 was cultured in the modifi ed RPMI1640 nutrient solutions containing either 30, 60 and 120 nmol/L FA or 5-MeTHF. Bisulfi te sequencing PCR was employed to detect the methylation status of Alu and LINE-1 after 20 days. Results The methylation levels of Alu and LINE-1 were increased with the concentrations increasing of FA or 5-MeTHF and were signifi cantly higher at 120 nmol/L of FA or 5-MeTHF than those at 30 or 60 nmol/L (P < 0.01-0.05). The methylation levels of LINE-1 at 60 and 120 nmol/L of 5-MeTHF groups were signifi cantly higher than that of FA. Conclusion There was a positive correlation between FA or 5-MeTHF and human genomic DNA methylation. 5-MeTHF was more effi cient on the methylation profi le maintaining than FA in human lymphoblast cell line.