Aim\ To study the factors influencing assembling quality of product under the condition of DFA (Desing for Assembly)
and carry through the evaluation. Methods\ The crankshaft piston rod as an example is analysed. On the basis of the principle of design
the relation between assembling quality and assembling model as well as the importance of expressing the assembly feature in establishing system of assembling quality evaluation are pointed out. Results Assembling quality based on DFA is bulit. According to the theory and joining with the example
assembling quality in the DFA is specifically shown. Conclusion\ This theory is necessary for the all round implementation of DFA and it provides a theoretical basis for using it in the DFA lower end.