Our daily life is mainly distributed in three living spaces, namely the first space (living space), the second space (working space) and the third space (shopping and leisure place). To improve people's quality of life, we must consider three living spaces at the same time. The improvement of the quality of life is often manifested in the decrease of the stay time in the first and second living spaces and the increase of the activity time in the third living space. Library is the third space besides family and work, and knowledge has also become social knowledge. The construction of library's "third space" can start with environmental design, layout division, readers' activities and leisure services.