Aiming at the problem that Cellulars of 2-dot Quantum-dot Cellular Automata were easy to switch when signal was inverted in the vertical direction.A method to transfer the signal inverting operation from vertical to horizontal was proposed.A XOR gate of 2-dot QCA and a full adder based on the XOR gate structure were designed with this method. The simulation to the function of the circuit was given through the Genetic Simulated Annealing Algorithm based on the semiclassical model of QCA. The simulation results validated the feasibility and the validity of this method. Compared to the traditional 4-dot QCA, the 2-dot QCA takes advances of fewer amounts of the electrons and the quantum dots required by 25%, higher integration by6.2%.