The invention relates to the technical field of unmanned ships and provides a hybrid frogman early-warning method and device based on an unmanned ship and underwater vehicles. The method comprises the steps as follows: a first unmanned ship receives a sonar detection message for a designated area and transmits a sonar signal to a detection area; at least two underwater vehicles receive the sonar detection message for the designated area and release hydrophone sonar optical fibers in corresponding water areas, and the hydrophone sonar optical fibers are used for receiving a first sonar signal released by the first unmanned ship and a second sonar signal reflected by a frogman; the position information of the frogman is determined according to the first sonar signal and the second sonar signal fed back by each underwater vehicle. By means of the underwater vehicles carrying the hydrophone sonar optical fibers, the early-warning method assisting in detecting the frogman is provided, the detection range can be further enlarged under the condition of original sonar equipment and the work power, and the early-warning range of the unmanned ship can be enlarged.