The application discloses a frame of double-person baby carriage and a frame folding mechanism thereof. The frame folding mechanism comprises an upper link, a lower link, a middle upright rod, two upper supporting rods, two lower supporting rods and two foot frames. The upper link and the lower link are spaced apart in a vertical direction; the middle upright rod is vertically connected between the upper link and the lower link; first ends of the two upper supporting rods are pivotally connected to both ends of the upper link; first ends of the two lower supporting rods are pivotally connected to both ends of the lower link; the foot frames are arranged in a vertical direction, top ends of the foot frames are pivotally connected to second ends of the upper supporting rods, bottom ends of the foot frames are pivotally connected to second ends of the lower supporting rods.