Abstract: This paper presented a method of reversed phase high performance liquid chromatography to determine the germicide N,N-methylene-bi-(2-amino-5-mercapto-1,3,4-thidiazole)(MBAMT) and it’s decomposition product 2-amino-5-mercapto-1,3,4-thidiazole)(AMT). Recoveries of MBAMT and AMT were 90% and 94% respectively. The detected limits of concentration for water sample were 7.19nmol/l for MBAMT and 2.87nmol/l for AMT. The resolution between the peaks of MBAMT and AMT was 2.5. The column efficiency and detected sensitivity of this method were significantly better in comparision with normal phase chromatography.