The invention relates to a serum combination marker for evaluating the gliclazide applicability of type 2 diabetes mellitus and a detection kit thereof, in particular to novel application of small-molecule metabolites, namely galactose, 5,8,11,14,17-eicosapentaenoic acid, 8,11,14-epoxyeicosatrienoic acid methyl ester and methyl palmitate, in serum samples in preparing the kit used for evaluating the gliclazide applicability of subjects as combination markers. The invention further relates to a kit for detecting patients remarkably responding to gliclazide in the subjects. By detecting relativeconcentrations of the combination markers in the serum samples of the subjects, the variables of the combination markers are calculated on the basis of a binary logic regression equation, and then onthe basis of determined section values, whether or not the subjects are suitable for gliclazide treatment is judged. The kit can achieve high-sensitivity high-efficiency detection of the small-molecule metabolites, and has the advantages of being low in detection cost, good in repeatability and high in diagnosis sensitivity.