The invention provides a beacon having a fish-finding function. The beacon having the fish-finding function comprises a lamp holder, a support, a battery chamber, an instrument chamber and a buoy, wherein the lamp holder, the support, the battery chamber, the instrument chamber and the buoy are connected in sequence from top to bottom. The lamp holder comprises a lamp shade and a lamp tube. The lamp tube is arranged in the lamp shade. A storage battery is arranged in the battery chamber. A solar cell panel is arranged outside the battery chamber annularly in a surrounding manner. The solar cell panel is connected with the storage battery. A positioning module, a single-chip microcomputer and a data transmission module are arranged in the instrument chamber. The positioning module, the single-chip microcomputer and the data transmission module are connected with the storage battery. The positioning module and the data transmission module are connected with the single-chip microcomputer. Fish-finding sonar is arranged on the lower portion of the buoy. The fish-finding sonar is connected with the single-chip microcomputer and the storage battery. The beacon is provided with the fish-finding sonar and can continuously detect fish schools; and because the beacons are widely distributed on shipping lanes, the activity routines and the distribution conditions of the fish schools can be effectively grasped, the function of the beacon is expanded, and the fish-finding cost is reduced.