Abstract: The Problem Discrimination and Resolving of the VG-354 Mass Spectrometer Magnet Part DACLir Haichen; Tu Xianglin (Institute of Guangzhou Geological New Technology, Chinese Academy of Sciences, Guangzhou 510640, China )Abstract:The problem discrimination of the VG354 MS magnet part DAC was introduced,and also a new measureing method through varing accelerating voltage with special for the DAC was devoloped which soloved the measuring diffculties of some isotopes such as U and Pb because of the DAC trouble.Keywords: magnet part, trouble, discrimination, measure