A multifunctional small dining chair, comprising a front U-shaped support frame, a rear U-shaped support frame, a seat, a backrest, a left armrest, a right armrest and a dining tray, wherein a top of the front U-shaped support frame and a top of the rear U-shaped support frame are arranged in a foldable manner; the seat and the backrest are arranged inside the front U-shaped support frame; the seat and the front U-shaped support frame are arranged in a foldable manner; a bottom end of the backrest and a rear end of the seat are hinged; a rear end of the left armrest and a rear end of the right armrest are connected to an upper front end of the front U-shaped support frame; and the dining tray is provided between the left armrest and the right armrest, and the dining tray is rotatable relative to the left armrest or the right armrest; the dining tray is detachably connected to the left armrest and the right armrest, and characterized in that a bottom of the dining tray is provided with a left inserting rod and a right inserting rod; a front end of the left armrest is provided with a left rod groove, wherein the left inserting rod is inserted into the left rod groove; a front end of the right armrest is provided with a right rod groove, wherein the right inserting rod is inserted into the right rod groove; a front end of the right inserting rod is provided with a disc; a right bottom end of the dining tray is provided with a disc groove adapted to the disc, and the disc is located in the disc groove; a right end of the disc groove is open; the disc is open-top and hollow inside; three arc-shaped through grooves are uniformly arranged on a bottom of the disc; a protruding post is provided at a center of an inner bottom surface of the disc; the protruding post is provided with a shaft hole being vertically hollow; a bottom cover is provided under the disc; a top surface of the bottom cover is provided with a lower shaft post and three threaded posts; an inner top surface of the disc groove is provided with an upper shaft post and three connecting posts; the lower shaft post is located at a center of the top surface of the bottom cover; the upper shaft post is located at a center of the inner top surface of the disc groove; a bottom of the upper shaft post is provided with a first post hole; a top of the lower shaft post passes through the shaft hole to be located in the first post hole; a bottom surface of each connecting post of the three connecting posts is provided with a second post hole; each threaded post of the three threaded posts corresponds to one arc-shaped through groove and one connecting post; a top of each threaded post passes through an arc-shaped through groove corresponding to each threaded post to be located in a second post hole corresponding to each threaded post; and each connecting post and each threaded post corresponding to each connecting post are connected by a screw, wherein each of the left inserting rod and the right inserting rod is provided with an elastic clamping button; a bottom of the elastic clamping button passes through a bottom of each of the left inserting rod and the right inserting rod; each of a bottom surface of the left armrest and a bottom surface of the right armrest is provided with a clamping button groove; and the bottom of the elastic clamping button is located in the clamping button groove.