Abstract: Determination of N-methyl piperazine in the water by direct injection gas chromatography (GC).The method completed the whole analytic process in 3 min.The N-methyl piperazine has been determinated by capollary column GC/FID with direct injection.The sample is qualitatively determined by retention time and quantitatively determined by peak-height extend standard method.When the average concentration range is 8.44～80.32 mg/L,the relative deviation is 1.8%～2.9%,and the standard deviation is 0.19～1.50 mg/L.The recovery rate of sample is 81%,the correlation coefficient is 0.9992,and the determination limit is 0.08 mg/L.