The growth design is a new top-down design method for mechanical product conceptual design based on the decomposition and reconstruction of function surface. The reconstitution of function surface, determining the number, the style and the relationship of function surface are the key of conceptual structure in the process of growth design. It is the constraint of the manufacturability of the part structure. Due to the lack of the related knowledge, it is the barrier to improve the efficiency of the growth design. The position relationship, the joint mode and manufacturability of function surface are analyzed comprehensively in this paper. According to the actual technical knowledge, the methodology of determining the position relationship and joint mode concurrently is proposed. So manufacture technical knowledge is introduced into the product conceptual design stage. It can improve the efficiency of growth design process, and feasibility is proved by specific case.