Abstract: In the new historical time,the thinese are constructing a harmonious society and must, pay close attention to the disadvantaged groups＇survival situation, from analysing the main composition of urban disadvantaged groups, This text points out that it is the duty-bound responsibility of the library to provide the knowledge assistance to the disadvantaged groups, and explains the concrete action that the library serve disadvantaged groups from four respects.

Key words: Harmonious Society, Library, Disadvantaged Groups Knowledge Assistance