The invention discloses a transaction processing method, a system, and a device based on a unified message and a storage medium. The method comprises steps: a front-end module configures messages of different business types to a unified XML (Extensible Markup Language) message according to a pre-defined unified XML message rule, and the unified XML message is transmitted to a back-end module; the back-end module receives the XML message and transmits the XML message to a third-party system corresponding to the XML message; and the third-party system carries out transaction processing according to the XML message, and information is returned. Through adopting the unified XML message, standardized management of the message can be realized, and the bank transaction extensibility and the working efficiency are improved.