The space design of small and medium size residential units is been as research subjects in this paper, through analyzing the design method of small and medium size residential units from the view of residential space design adaptability, and analyzing living lifestyle of the main residence in small and medium size residential units, this paper summed up the principles of space ambiguity, indoor environment comfortable, personalized living space and complete public facilities of small and medium size residential units design, and proposed the flexibility and adaptability, minute integration space design methods of small and medium size residential units.