interesting phenomenon, the thickening and thinning of polymer films in the water media, was investigated in this paper. The studied polymer films were cast from atactic poly(R,S-3-hydroxybutyrate)/poly(4-vinylphenol) (PVPh) and syndiotactic poly(R,S-3-hydroxybutyrate)/PVPh blends solution. The physical properties of the blend films were characterized by differential scanning calorimetry (DSC), and the hydrogen-bonding network in the blends was characterized with the employment of Fourier transform infrared spectroscopy (FT-IR). The thickening and thinning process of the polymer films in water media was monitored by the measurement of the thickness. The effects of temperature and surfactants on the process were evaluated, furthermore, and the essence of the thickening and thinning of the polymer films was discussed.