The invention discloses a communication message synchronization method and device, and belongs to the technical field of the internet. The method comprises the steps of: acquiring n communication messages to be synchronized in a first social application client and a message type of each communication message; for each communication message, generating message data including the message types of the communication messages and message contents of the communication messages; and by using a message block as the unit, synchronizing the n pieces of generated message data to a second social application client. Each message block corresponds to at least one piece of message data; when each message block corresponds to at least two pieces of message data, the communication messages corresponding to the at least two pieces of message data belong to the same session; the second social application client and the first social application client have the same type and share the same social account; and the communication message synchronization method and device solve the problem that in the prior art, after the communication messages are synchronized to other platforms, the social application clients in other platforms possibly cannot identify the communication messages.