The purpose of this study is to identify an acquisition material duplication rate among three academic libraries for developing an academic library network. Three academic libraries located in Gyonggi-do, Korea were selected for data collection. The acquisition lists in both 2000 and 2001 were compared and analyzed between two libraries respectively. The results show that the duplication rate is 0.4% in 2000 and 2.8% in 2001 between medium size libraries, and 1.33%, 1.11% in 2000 and 3.63%, 3.88% in 2001 between a big size library and medium size libraries. These tell us that a big library can get benefit from a library network with medium size libraries.