The invention relates to a large-work-space controllable-mechanism stacker crane. The stacker crane comprises a large-arm swing branch chain, a mid-arm swing branch chain, a small-arm swing branch chain, a posture keeping branch chain, an end executor and a rack. A robot completes carrying stacking operations with large work space and flexible changeable track output through the combined movement of the large-arm swing branch chain, the mid-arm swing branch chain and the small-arm swing branch chain. Three groups of parallelogram structures of the posture keeping branch chain can guarantee that the end executor keeps a horizontal state constantly in a working process, and all servo motors are mounted on the rack, bars can be made into light bars, the robot moving inertia is small, the dynamic performance is good, and requirements for high-speed and heavy-duty carrying and stacking can be well met. According to the stacker crane, a novel connection rod mechanism is utilized, so that the carrying and stacking work space is large, the connection rod transmission mechanism is simple, stresses on the bars are improved, and the manufacture of large stacker crane is applicable.