In this study, the toxic effect of cadmium on extracellular Na + , K + , and Ca 2+ in the gill and small intestine of goldfish Carassius auratus was determined with the technique of ion chromatograph. Two-way ANOVA indicated that the two factors (Cd 2+ treatment and time) and the interaction factor had significant effect on the level of Na + , K + , and Ca 2+ in the small intestine and gill. 1.0mg/L Cd 2+ significantly increased Ca 2+ level in the small intestine, but Ca 2+ level in the gill was significantly decreased by 1.0 and 5.0mg/L Cd 2+ at 24, 48, and 72h. Na + and K + level in the small intestine and gill was increased by 1.0mg/L Cd 2+ at three time points, but increased by 5.0mg/L Cd 2+ at a certain different time. In addition, Na + level was significantly decreased by 5.0mg/L Cd 2+ at 24 or 48h in the small intestine and gill. The results indicated that Cd 2+ played an important role in regulating the level of Na + , K + , and Ca 2+ in the small intestine and gill of goldfish C. auratus. A method was constructed to investigate the extracellular Na + , K + and Ca 2+ in the tissues of gold fish with ion chromatography.