Abstract: Stanozolol and Furazabol can be used as doping agents in sports, their behavior in tandem mass spectromater is also interesting. Both of Them have high intense m/z 270 ions in Their CID spectra, but they have totally different structure and origins. the m/z 270 ion of Stanozolol is a Distonic ion; the formation of Furazabol m/z 270 ion involves the elimination of CH2CHCH3 through methyl transfer.