The secondary circuit digitization based on network is the developing trend of the smart substation, which facilitates the data sharing, while brings some hidden trouble to the safety and stability of the secondary equipment due to data abnormality such as network storm. In this paper, the main problems affecting the reliability of data transmission are analyzed and the message management technology based on data flow control is put forward, which can effectively improve the reliability of data transmission. A solution based on cross-network port flow control is also proposed for cross-network data exchange. This work is supported by Science and Technology Project of the Headquarter of State Grid Corporation of China (No. JB71-16-008).