The invention discloses a method, a device and a system for encapsulating and de-encapsulating messages. The method for encapsulating the messages comprises the steps of receiving a first message and obtaining a second message according to the first encapsulated message, wherein the second message comprises a payload part and first control information; the payload part comprises the step of stripping the contents of a preamble PRE domain and a frame start delimiter (SFD) rear domain of an Ethernet message when the first message is the Ethernet message; and the first control information only comprises a frame header cHDR (High Date Rate) domain which at least comprises a length indicator PLI(Programming Language Interface) domain containing a payload byte, so that a de-encapsulation end receives the second message and acquires a data message with corresponding length according to the PLI(Programming Language Interface) domain in the second message. The embodiment of the invention can reduce a redundant byte encapsulated by the Ethernet message.