The preset invention relates to a new use of an antimicrobial peptide, a functional derivate, fragment or variant thereof for treating a gastric ulcer, preventing or treating an infection of H. pylori, particularly multidrug resistant H. pylori, wherein the antimicrobial peptide is selected from the group consisting of Epinecidin-1 (Epi-1), tilapia piscidins (TPs) and combination thereof.本發明係關於一種抗微生物胜肽、該抗微生物胜肽之功能性衍生物、片段或變體用於治療胃潰瘍、預防或治療幽門螺旋桿菌(特別是多重抗藥性幽門螺旋桿菌)感染的新用途,其中該抗微生物胜肽係選自由石斑魚抗菌胜肽-1(Epi-1)、吳郭魚抗菌胜肽(TPs)、及上述之組合所組成之群組。