Rosin-alum sizing has been very important in papermaking since it was developed by Morits Illig in 1807. But effect of alum is varied by pH condition very significantly. Therefore rosin sizing has limited in acid condition. So cellulose reactive sizing agents were developed and used papermaking industry. But they have so many problems and concern for rosin sizing in neutral pH condition is increased. In this study, we attempt to confirm the possibility of rosin sizing in neutral pH condition with cupric ion and C-PAM as mordant.