We present a “master-slave-response” synchronization system of chaotic multiple-quantum-well lasers. And we study the applications of chaotic parallel synchronization for optical logic gates. An injection multiple-quantum-well laser drives two responding systems of multiple-quantum-well lasers to obtain chaotic synchronization while the injection multiple-quantum-well laser can synchronize the responding systems. We present theoretically the constructions of the fundamental all-optical gates based on the parallel synchronization of responding systems and define their computational principle. By modulating the driving light into the responding systems, all-optical logic gates characterizing logic function are realized by synchronizing or unsynchronizing appropriately the two chaotic states of responding systems. We present all-optical XNOR, NOR, NOT logic gates and their logic computational methods. Numerical simulation result validates the feasibility of the system.