Abstract: Against the background of continuous expansion of the complexity theory and aesthetic intention, the space, the form and the epidermis design of many buildings were combined with digital technology, breaking through the constraints of the original paradigm and design methods, showing a trend of complexity and diversity. In particular, the formation logic and expression form of architectural forms and skins showed the complexity characteristics of nonlinear and dynamic changes. Taking the complexity of architecture as the starting point,the form and epidermis design method of complex architecture was studied and analyzed. Combined with the design practice of large-scale public buildings such as sport activity centers, the digital design process and optimization content of complex architectural forms and skins were explored taking "geometric fractal" and "emergence generation" in the complexity theory as the main design concept. In the technical method, the shaping effect of the digital design program based on the design concept on the overall forms and epidermis of buildings was emphasized, and its expression in line with the contemporary technical aesthetics was studied, and reference to the design strategy of complex architectural forms and epidermis combined with the idea of digital design was provided.