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A new spectrophotometric sequential injection （SI） base-acid titration system was developed for the determination of different kinds of strong acid, weak acid, strong base, carbonate and hydrogen carbonate, using bromothymol blue as indicator firstly. The samples such as hydrochloric acid, sodium hydroxide, vinegar, drink, calcined soda and sodium bicarbonate were titrated, determined by a spectrophotometric sequential injection system. The results evaluated with manual titration method by t-test at 95% confidence level were not significantly different.In the first section, a review on the development of titration using flow injection system, sequential injection system and multisyringe flow injection analysis （MSFIA） was made. The emphasis was put on the application of sequential injection titration in different areas.In the second section, an introduction of my work about the strong acid and weak acid titrated by a spectrophotometric sequential injection system was made, using bromothymol blue （BTB） as indicator. The hydrochloric acid samples were firstly titrated against sodium hydroxide zone contained BTB. The change of the BTB color was monitored at 620 nm. Four linear relationships between the peak area and the logarithm of acid concentration were obtained in the range of 4.0×10-53.00mol/L hydrochloric acid. The influence of wavelength, reaction coil length, carrier stream flow rate, acid and base zone volumes, titrant concentration and BTB volume on the range of the method were studied to obtain an optimum. The sample frequency was 30 samples.h"1. Secondly, the acetic acid and citric acid were titrated based on the hydroxide acid experiments, with the same indicator and the wavelength, etc. Three linear relationships between the peak area of the unreacted base and logarithm of the acid concentration were obtained in the ranges of 0.202.0mol/L acetic acid, 1.0×10-4 1.0×10-3mol/Lacetic acid and 3.3×10-31.7×10-2mol/L citric acid. The system was
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