Abstract: PVT property under real molding conditions was obtained through a on-line tester of polymer materials, so injection material shrinkage could be achieved and was used for mold design. In addition, the mold size was also calculated，which was based on off-line PVT property parameters. The numerical simulation method was used for simulating the above-mentioned two kinds of mold size so that mold precision could be analyzed comparatively. It showed that the product dimension precision based on on-line PVT test results were closer to the actual ones.

Key words: polymer material, pressure-volume-temperature property, on-line test, mold design, dimension precision