Abstract: Chloride ion reacts with mercuric thiocyanate and iron (II) nitrite in acidic media to form a red complex, and the absorbance corresponding to the complex will be proportional to the concentration of chloride. According to the principle, a automatic analytical method used for determining ppb-level chloride has been established by flow-injection spectrophotometry. Based on this method, a flow-injection spectrophotometric method for the performance determination of strong alkaline anion-exchange resin (SAAER) has been developed. The performance of SAAER (201x7 type) was determined, the effects on the exchange capacity of 201x7 type resin, the concentration, using mount and flow rate of regeneration reagent, the flow rate of sample water, ion-exchange temperature, etc. were investigated dynamically. The optimum conditions being suitable for 201x7 resins were obtained. The method is characterized with small device, shorter test-time, simplicity to operate, and good reproducibility. It is more efficient than the manual method, and it is able to apply for the determination of 201x7 type resin performance.