The present invention are an autonomous parameter change communication synchronization method and system based on an external clock. The method comprises: firstly, two communication parties acquiring the same external clock source signal, and each correcting a local time according to the external clock source signal; secondly, a communication caller autonomously establishing a bidirectional communication link with a communication responder by means of a call response mechanism; then the two communication parties entering an autonomous parameter change communication stage, and changing respective system sending and receiving parameters according to synchronous clock; and at the same time, the two communication parties each performing comparison to determine a time difference value at a parameter change moment in real time, and each correcting a local clock when the difference value is greater than a preset threshold value, thereby maintaining the consistency of the local clocks of the two parties.