The contents is a important factor in the digital library. and lots of contents are needed to collect. The materials needed for preservation are selected for contents from the  selection criteria which are limited by the copy right law.  And libraries are digitalizing paper materials for preservation. The digitalized materials are used for contents of digital library. By these situations, digital library is regarded having a preservation effect. This study analyzes digital library and contents with the view of preservation, and suggests what library should do for preservation.