Abstract: A Study on the Mass pectrometry of Nonaromatic 1,2,4－ triazinesSao Yaowu(Department of Chemistry,Tsinghua Universety，Beijing 100084,China)Cai Mengshen（School of Pharmaceutical Sciences，Beijing Medical University,Beijing 100083,China)Pang Jibal;Huang Liru;Peng Jiarou(Analytical Center of Beijing Medical Universety，Beijing 100083,China)Abstract:The mass spectrometryoften nonaromatic1,2,4—triazines was studied.The b-efragmentation was popular.6-ethoxycarbonyl-3-thioio-5-hydroxy-1,2,4-tri－azine was studied with EI-MIKES method.b-e and a-c and other rine fragmenta－tions were found in the spedes formed from the disassociation of 6-substituent.Keywords:mass Spectrometry,1,2,4-triazine,b- e fragmentation,a-c fragmentation