People are talking about “sustainability” these days. With the development of the economy in China, great changes have taken place in the dwelling modes and small units have gradually become an important component of city life. Obviously, dwelling space with different users has significant differences. Through analysis based on small dwelling units of different users, we can find that: if we take the possibility of development and change into account at the beginning of the planning or design, the dwelling space will be adapt to social development and changes in family structure. We can achieve the goal of "sustainable" development besides the technological approaches.