The invention discloses a method, a device and a system for power line carrier communication with dynamic adjustable rate. The method at a sending terminal comprises the following steps: acquiring a to-be-sent data packet and dynamically confirming a target information rate; confirming an information frame according to a preset frame structure, wherein the information frame includes an information frame header and information data, the information frame header comprises the target information rate and the information data contains a data packet; performing spread spectrum coding treatment on the information frame header according to a preset minimal information rate and performing spread spectrum coding treatment on the information data according to the target information rate; sending the information frame after the spread spectrum coding treatment to a receiving terminal. According to the method, the receiving terminal can extremely receive the information frame header; the target information rate can be dynamically adjusted according to the condition of a channel, so that the all-weather communication accessibility can be guaranteed; the transmission at different information rates can be dynamically realized under a same bandwidth condition; the bandwidth can be maximally utilized; the communication rate and the success rate can be guaranteed.