The invention belongs to the technical field of underwater sensor networks and provides a media access control method based on motion prediction. Four kinds of messages of RTS, CTS, DATA and ACK are used for communication, all nodes broadcast signals randomly, according to received signal transmission time and known transmission speed, each node computes the distance between the node and an adjacent node, the obtained distance between the node and the adjacent node is broadcast, accordingly, each node records the distance values between all of the nodes, and a distance matrix D is used for representation; through the current speed and the previous motion speed of the nodes, the motion speed in the future of the nodes is subjected to linear prediction, then the distance values in the distance matrix D are updated, the maximum value in the distance matrix D is obtained, and reservation slot length is computed; and communication is carried out through a sub-slot reservation transmitting mechanism. On the basis that communication conflict between the nodes is avoided, slot resources are fully used, and channel using rate is improved.