Disclosed is a device for replacing an electrode under the ship navigation state. An inner cylinder and an outer cylinder are tightly matched, a sealing layer is arranged between the inner cylinder and the outer cylinder, outer groove openings are symmetrically formed in the outer cylinder, inner groove openings corresponding to the outer groove openings are symmetrically formed in the inner cylinder, an inner cylinder gland compresses the upper end face of the inner cylinder, the inner cylinder gland and the upper end face of the outer cylinder are fixedly connected into a whole through a bolt, an electrode tip is arranged in the upper end face of the inner cylinder, the lower end of the electrode tip is connected with an electrode bar contained in the inner cylinder, a gap between the electrode tip and the inner cylinder gland is filled with sealing packing, a packing gland compresses the sealing packing, the packing gland and the inner cylinder gland are fixedly connected into a whole through a bolt, the upper end of the electrode tip is sealed by a cable flange, and a cable penetrates through the cable flange and is connected with the electrode tip. The device solves the problems that due to the facts that a ship sea water tank electrolyzes an anti-corrosion and anti-fouling electrode device, and a new electrode can not be timely replaced, a ship pipeline is blocked, a ship sea water pipe is worn out, and the ship performance and the safety decline, or due to the fact that the ship must be docking to replace the new electrode, the high maintenance cost is paid.