A fixture block composite structure for workpiece positioning comprises a fixture block group composed of at least a stop fixture block and at least a one-sided movable fixture block. The stop fixture block is fixed to a base by a plurality of mountings, and two opposite lateral sides of the stop fixture block in the extending direction of base are provided with a fixed upright positioning plane respectively. The one-sided movable fixture block has a fixed holder, the holder is fixed to the base by a plurality of mountings. The holder is provided with a movable piece which can be driven to reciprocate towards the positioning plane on the stop fixture block. The movable piece is provided with a clamping surface on one side facing the positioning plane.