The invention discloses a lattice type frame welding clamp. The clamp comprises structures such as a machining platform, horizontal positioning rods and vertical positioning rods; assembling holes forpositioning and installing are formed in the machining platform, the horizontal positioning rods are fixed on the upper surface of the machining platform, the assembling holes are distributed in thedirection of the horizontal positioning rods, and positioning scales are arranged on the horizontal positioning rods; and the vertical positioning rods are positioned through the positioning scales onthe horizontal positioning rods, the bottoms of the vertical positioning rods are fixed to the machining platform through the assembling holes, and the tops of the vertical positioning rods are usedfor positioning the position of a truss. The length of each horizontal positioning rod is matched with the size of a frame, the vertical positioning rods are distributed along the horizontal positioning rods according to the size and the structural design of the frame, the whole frame structure can be machined at one time, the unified reference standard is provided integrally, and the machining precision is improved; and for the clamp, the positions of the vertical positioning rods are determined through the assembling holes, and the relatively high precision can be achieved as long as the positions of the assembling holes and the lengths of the vertical positioning rods are ensured to be accurate.