The invention provides a drill floor mechanical arm clamping mechanism. The drill floor mechanical arm clamping mechanism comprises a clamp body, an opening and closing cylinder body and opening and closing piston combination, paws, a paw cylinder body and paw piston combination, a paw front baffle block and a small connecting rod. Two mutually symmetric long-strip-shaped grooves are formed in theclamp body. The two paws are of the same structure and are symmetrically arranged. Bases of the two paws are arranged on the two long-strip-shaped grooves in the upper surface of the clamp body. Thetwo ends of the opening and closing cylinder body and opening and closing piston combination are fixedly connected with the bases of the two paws. Arms of the paws are of hollow structures. The paw cylinder body and paw piston combination is arranged in hollow interiors of the arms. The tail portions of paw front stop blocks are hinged to the upper portions of the arms. The middle sections of thepaw front stop blocks are hinged to the extension ends of the paw pistons through small connecting rods. The drill floor mechanical arm clamping mechanism is compact in structure, adopts hydraulic driving, is safe, reliable, stable in work and capable of adapting to tubular columns with different diameters in a certain range, effectively reduces the labor intensity of operators, and improves the working efficiency and the safety.