The Fourier transform infrared (FTIR) results are consistent with the differential scanning calorimetric results and verify the anomalous crystallization of water in 50% poly(vinyl methyl ether) aqueous solution during heating. Below about -34 degreesC, the water/polymer complex was not damaged, and the water still associated with the polymer. When heating to about -34 degreesC, the associated water started to free from the unpolar (methyl group) and polar-site (ether-oxygen group) interaction fields of polymer gradually. Then crystallization of water was induced in this system at temperatures ranging from -34 to -24 degreesC. The FTIR data also indicate that the structure of water started to change first upon forming strong H bonds among water molecules, and then the dehydration of the polymer began to proceed subsequently when the anomalous crystallization of water occurred.