The invention relates to a message load balancing method of a 1553B bus, and belongs to the technical fields of avionics and satellite navigation. The method performs rational organization on transmitted 1553B message blocks. Specifically, message transmission major cycle (maximum transmission cycle) and a minor cycle (minimum transmission cycle) on the 1553B bus are firstly determined. In a major cycle, the shorter the cycle of information transmission is, the higher the transmission number is. Therefore, in load balancing scheduling of messages, balancing scheduling on transmission time phase is started from the shortest cycle in which transmission number is highest, and then the messages of the second shortest cycle are scheduled, until scheduling is completed. The scheduling method reduces average delay rate of the bus, balances bus load, and achieves optimal communication efficiency.