To study the effect of organic reagent as matrix moditicr tor eliminating the salt matrix mtertcrence and its mecnamsm, ascorbic acid, citric acid, tartaric acid and oxalic acid were used as matrix modifier in the determination of Pb, Ca and Cd by GFAAS. The analytical information before and after adding organic matrix modifiers were compared. After the addition of organic matrix modifiers, the atomization signal and background signal were separated, atomization temperatures decreased enormously, the ratios of atomization signal to background signal increased and the RSDs and recoveries of practical samples improved obviously, It was concluded that organic matrix modifiers can eliminate salt matrix interference effectively, The mechanism of the effect of the organic matrix modifiers is suggested to be caused by the reductive substances produced by the decomposition of the orgaaic additives as well as the complexing action and the melt-assisting action of the organic additives.