Abstract: The accurate mass analysis for common organic explosives of TNT, RDX, HMX, PETN were obtained by direct analysis in real-time ion source coupled with a time-of-flight mass spectrometry (DART-TOF MS). The result indicates that there is no guarantee to obtain the unique molecular formula of a compound even on a high resolution mass spectrometer with accurate mass measurement capabilities. By virtue of the specta accuracy in math with MassWorks isotope peak type, the identification accuracy of high-resolution flying-time mass for formula of target compound has been significantly improved. Thus according with more accurate determination of the chemical composition, the method can provide reference for high-resolution mass analysis of unknown compounds.