The coupling ratio (CR) is an important parameter that measures the mechanical behaviors of coupled walls (CWs). The design method using CR for CWs has been adopted gradually and internationally. To calculate CR in elastic and plastic stages and clarify a reasonable range for its application, a calculation method was proposed based on theoretical derivation and numerical simulation results. The variation of CR during elastic-plastic stage and the responses of CWs with different combinations of elastic and plastic CRs were analyzed. A theoretical formula for calculating top lateral displacement of CWs was put forward, and the suggestion on realizing ideal yielding mechanism for CWs by using CR was given. Results show that the calculation method of elastic and plastic CRs and the formula of top displacement were both effective and reasonable. The elastic CR was mainly controlled by the geometry of CWs, whereas the plastic CR had impacts on the ultimate strength and ductility of CWs, whose upper limit should thereby be set. The difference between plastic CR and elastic CR should be larger than 10% so as to avoid the occurrence of yielding in wall piers prior to most coupling beams. A safer and more reasonable design for CWs can be achieved by calculating and controlling CRs.