The utility model discloses an oil-immersed transformer which solves the problems that a transformer sealing oil leakage phenomenon is easy to occur to arouse increase of maintenance cost and reduction of the reliability problem of the transformer. The key points of the technical scheme are that the oil-immersed transformer comprises an oil box, a cover body arranged on the oil box and a tap switch arranged on the cover body, wherein the oil box is internally provided with a protection cavity; a limiting strip is arranged between the oil box and the cover body; a sealing component is arranged between the oil box and the limiting strip; an annular convex shoulder is arranged on one side, corresponding to the limiting strip, of the sealing component; an annular convex rib is attached to the outer surface, corresponding to the annular convex shoulder, of the limiting strip; the annular convex rib matches with the annular convex shoulder in a sealing manner; a hollow frame-shaped lock catch is hinged to the limiting strip; a locking tongue buckled with the lock catch is arranged on the sealing component; a groove connected with the lock catch in a supporting manner is arranged on the other side, relative to the limiting strip, of the locking tongue. The oil-immersed transformer prevents the oil-immersed transformer sealing oil leakage phenomenon efficiently through close adhesion between the limiting strip and the sealing component.