Abstract: Maltulosyl arginine is the initial maillard reaction product of maltose and arginine, which may have anti-diabetic activity. In this study, LC/MS was combined with ultrafiltration as a new method to investigate its inhibitory activity on maltase. The quantitative data was got from a triple quadrupole instrument in multiple reaction monitoring (MRM) mode. The experimental results proved that maltulosyl arginine is an effective maltase inhibitor and can be used for the treatment of diabetes and obesity.