The invention relates to a storage battery online replacement device. The storage battery online replacement device comprises an air switch I, a rectifier element, an air switch II, an electric current meter and a direct-current fuse which are connected in sequence through wires, the air switch I and the direct-current fuse are connected with a connector terminal respectively, two voltmeters are connected in parallel, one end of the voltmeters is connected to the input end of the rectifier element, and the other end of the voltmeters is connected to the output end of the direct-current fuse. According to the storage battery online replacement device, the situation of replacing a storage battery under the condition of supplying the electricity uninterruptedly becomes possible, the work reliability of a direct current system is enhanced, and the direct current system accidents are avoided.