The invention discloses an automotive body robot flexible welding system for mixed line production of multiple vehicle types. The system comprises a horizontal rotary clamp storing and supplying unit,a robot mounted on a fixed mounting base, a plurality of sled supporting and locating units for supporting and locating a workpiece and transporting the workpiece, a rolling machine unit for locatingand clamping the sled supporting and locating units and making the sled supporting and locating units move along a production line, a bottom plate locating, clamping and locking unit for locating andlocking the clamp released at the clamp working position by the robot and locating and clamping the workpiece, a workpiece storing unit for storing the workpiece and feeding back the detection signalof the stored workpiece applicable to corresponding vehicle type; and an electric automation control unit. The invention depends on the global control of the electric automation control unit, realizes the purpose that the workpiece and the clamp can be replaced and located automatically and quickly, and improves flexible capability for mixed line production of multiple vehicle types.