For representing the coupling relationships among various correlate elements in the formation process of assembly qualities, the mapping relations between the structure domain and the quality domain was established on the basis of analyzing the hybrid structure assembly. Through classifying the quality characteristics, the quality domain was divided into two sub-sets which are quality control points set and quality attributes set. Defining the relevant elements in the model, such as vertex, arc, etc by the theory of network flow, the coupling relations among various quality control points in the formation process of assembly qualities were reflected. According to the sequence of quality control points entering into assembly environment, their corresponding hierarchy in the model were determined, which presents the timing sexual of the formation process of assembly qualities. At last, a correlation-model between quality attributes and quality control points in the assembly process of complex product based on network flow was established, which would be the theoretical basis for the dynamic tolerance optimization of quality control points. An example of an automobile active gear axle assembly was given to demonstrate the feasibility of the correlation-model.