Abstract: According to the Coulomb's principle and photoclectricity to control the end point an automatic analysis instrument of carbonate content is designed. The basic principle of mis instrument is briefly introduced in thes article and the introduction of performance test is stressed.The accuracy of an high pure (99.9%%) standard carbonate determined is 0.08% and the precision is 0.87%.The analyticle performance of thes method compares well with that of other technique,e. g. the method of measuring pressure.Our test system is characterized with high precision,high speed and highly automatic operation. This analyzer can be widely used in the analysis of drposits and in the study of such fields as petroleum industry, sedimentology and quarternary geology.