The joint between all plains in unit sheet aluminum curtain wall which is hanged on main body architecture is plugboard combination. The change of ambient temperature and wind load generates the change of expansion joints, which are the performance index of curtain wall required gas and water tightness, among curtain walls and suspension members. Thus obtained value of expansion joint among curtain walls is very important to guide the curtain wall’s installation. Here, an assemble structure model of curtain wall has firstly been established, the changing law of expansion joints among curtain walls has also been obtained under all kinds of work conditions based on previous model and the ANSYS software’s application. Some better suggestions have been also provided associating the construction technical specification. It can provide future protection for revised this technical specification, and accelerate the scientific normalization of the design in construction curtain wall.