Poly(vinyl methyl ether) aqueous solution (30 wt.-%) at low temperature has been investigated by DSC and FTIR spectroscopy. Below -20degreesC, there are two types of ice formed by free water and frozen bound water respectively. When the ice formed by frozen bound water melts, the PVME begins to form hydrogen with water. A cooperative hydration phenomenon is observed in this system between -20 similar to -6degreesC during heating. FTIR data also show that hydrogen bonds between water molecules and polymer groups are broken completely before the cooperative hydration happens. This indicates that the unfrozen bound might not exist in 30 wt.-% PVME aqueous solution at low temperature.