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Objective In order to deal with the potential security threats caused by the complex connections between various subsystems in urban rail transit system, China Urban Rail Transit Association proposes that physical security isolation should be implemented between the safety production network and the external service network. Under the existing transmission method, problems such as packet loss and bit error often occur during one-way data transmission, and new methods need to be sought to improve the reliability of one-way data transmission in urban rail transit. Method The transmission principle and existing problems of the one-way security isolation system, as well as the proxy and session configuration in the one-way security gateway are described. The judgment methods of three types of transmission anomalies (proxy order disorder, session order confusion and transmission timeout) are analyzed. A data transmission method based on information backup is proposed, and the header format of backup information is built. The technical process of checking transmission anomalies by the data transmission method based on information backup technology is formulated, which is verified by experiments. Result & Conclusion This method can effectively solve the problem of low reliability of one-way data transmission of urban rail transit.