The PVT data of five kinds of biaxially oriented polypropylene (BOPP) Resins was measured by the PVT-100 apparatus．Thermal expansion coefficients (α) and isothermal compressibility (β) were evaluated from Tait equation in the melting state and then compared with those fitted with the value of experiment．The results showed that it was reasonable to calculate α and β with Tait equation in the melting state．At the same time

it was found that thermal expansion coefficients

isothermal compressibility and the melting temperature (Tm) of one of BOPP melts (S28C) were lower than those of the others in the same test conditions

indicating that the volume deformation of S28C resin is less so that it could be realized to avoid arising surface defects of the film (biaxially oriented polypropylene film) due to contracting

thereby decrease damage to the film in the subsequence process．Accordingly superior processing properties of S28C resin are confirmed from PVT speciality．