The invention relates to a foundation support horizontal regulating device. The foundation support horizontal regulating device comprises a fastening structure for being connected with a ship platformand a horizontal regulating mechanism which is fixedly connected with the fastening structure, wherein a height regulating mechanism is arranged on the horizontal regulating mechanism; the horizontalregulating mechanism can adjust the horizontal position of the height regulating mechanism; the height regulating mechanism comprises a first clamping chuck which is detachably connected with the horizontal regulating mechanism; and an ejector rod is arranged on the first clamping chuck, and can move up and down to prop a foundation support. According to the foundation support horizontal regulating device disclosed by the invention, the horizontal position of the ejector rod can be horizontally and rotatably regulated, and the ejector rod can move up and down, so that the horizontal planenessof the foundation support can be propped; the regulating accuracy is more accurate; surplus quantity lineation cutting by the foundation support horizontal regulating device is more convenient, and the risk that a deck surface is cut, and the deck is damaged is effectively reduced.