The process of transforming the combinatorial complexity in the system to the periodic one which contained in the complexity theory based on axiomatic design put forward by Suh was analyzed. Meanwhile, through the integration of c/p transformation and TRIZ theory, a design model for the combinatorial complexity elimination process was proposed. Firstly, the combinatorial complexity exists in the system was judged, and the functional structure to determine the functions that led to the time-dependent combinatorial complexity of the system was drawn. Then, the functions were analyzed with TRIZ tools, and a reasonable combinatorial complexity of the functional period was put forward. Finally, the virtual functional period description was transformed to an improved design plan. It was verified by the engineering practice of “capacitive online thickness measurement system”.