Abstract: The El mass sprctra of organophosphorus compounds containing tyraminyl radical were studied by means of high resolution and metastable defocusing MS technique. Mechanism of the free radical and positive charge of nitrogen and sulfur atoms induce cleavage have been investigated, the regular pattern of El spectroscopy was reported. Most base peaks are formed from β cleavage of nitrogen atom. When alkyloxy substituent and aryloxy substituent were linked togather with tyramine thiophosphoryl, the exchange of sulfur atom and oxygen atom always takes place on aryloxy substituent, then P-S bond cleavages and forms arylthioyl fragment.