The invention discloses a foldable bilge keel with a groove-shaped base plate. The foldable bilge keel comprises the base plate and a rotary plate. The base plate is formed by connecting two structural styles, namely, base plate convex plates and base plate concave plates, in a staggered mode. A shaft sleeve is welded to the outer edge of the base plate, and a rotary shaft is arranged in the shaft sleeve. The rotary plate is composed of an inner plate and a cover plate, one end of the inner plate and one end of the cover plate are in rigid connection with the rotary shaft, the inner plate and the cover plate are arranged in a V shape, the inner plate is formed by connecting two structural styles, namely, inner plate convex plates and inner plate concave plates, in a staggered mode, the inner plate convex plates and the inner plate concave plates correspond to the base plate convex plates and the base plate concave plates in position, and therefore the inner plate can be attached to the base plate after rotating around the rotary shaft. The cover plate is a flat and straight plate, a front supporting box and a rear control box are fixed to the two ends of the rotary shaft through shaft sleeves in a welded mode, the shaft sleeves are rotatably connected with the rotary shaft, a rotary shaft driving device is arranged in the rear control box, and the rotary shaft is connected with the rotary shaft driving device. According to the structure, a folding state can be adopted in a limited channel or small wind waves, and damage such as grounding and collisions is avoided.