The crystallization behaviors and crystallization kinetics of iPP in pressure field were investigated by confining-fluid pressure-volume-temperature (PVT) measurement technique.The absolute specific volume of the polymer can be obtained by correcting the relative volume difference with the specific volume of the confining fluid.So it was an effective method by confining-fluid pressure-volume-temperature (PVT) measurement to catch information of crystallization of semicrystalline polymers.The results revealed that molecular chain of iPP was introduced more easily into crystal lattice with powerful free energy of molecular chain improved by pressure field so as to improve the crystallization temperature and crystallization speed.Formula of crystallization temperature with pressure was found by means of data fitting.It was attempted to build a crystallization kinetics model by improving Jeziorny equation which can forecast the crystallization process of the iPP in pressure environment.The results showed that crystallization curves can be suitable for explaining some changes of the crystallization of iPP when crystallinity exceeded 0.08.Growth pattern of crystallization accorded with the behavior of 2-dimensional crystallites.Decrease of free volume was one of the main causes for the increase of crystallization rate.