The invention provides a rule-based automatic auditing system. The automatic auditing system comprises a business system part, a data transmission device and an auditing system part, which are sequentially connected, wherein the business system part comprises a plurality of business systems, each business system comprises a business system database and a data extracting device, the business system database is connected with the data transmission device through the data extracting device, the data transmission device is used for transmitting data prepared by all the business systems to a data receiving device of the auditing system part through an internet at regular intervals, and the auditing system part comprises the data receiving device, a database to be checked, a checking analyzing component, a rule engine, a doubtful point database, and a checked database. The rule-based automatic auditing system can continue auditing and monitoring automatically, can find abnormal data in a large number of business data automatically, improves the auditing efficiency, and can customize check rules; furthermore, the rule definition is described with natural language and is simple and easy to understand, so that the application range of the customized check rules is enlarged.