The invention discloses a flexible clamp for car door welding. Clamping mechanisms are arranged aiming at car door workpieces of different types, and positioning blocks and pressing blocks of the different clamping mechanisms are matched with positioning hook faces of the car door workpieces of the corresponding specifications. The positioning blocks are mounted on a first mounting frame around first rotary shafts, the pressing blocks are mounted on a second mounting frame around second rotary shafts, and thus the positioning block and the pressing block belonging to the same clamping mechanism can be located at a work position or a vacant position at the same time through rotary switching of the first rotary shafts and the second rotary shafts. When the positioning block and the pressingblock belonging to the same clamping mechanism are both located at the work position, the positioning block and the pressing block clamp and fix the locating hook faces of the car door workpieces of the corresponding types. Thus, the flexible clamp for car door welding can meet the clamping and positioning requirements of the car door workpieces of multiple specifications, the production input cost can be effectively reduced, the car research and development production period can be shortened, and the market competitiveness and economic benefits of enterprises can be improved.