Abstract: The PVT data of reservoir fluids are mainly influenced by the reservoir temperature, pressure and the composition of formation crude. The PVT data of three different crude oil samples obtained from Tahe oilfield in Tarim basin and Chunliang field in Shengli oilfield are measured in detail in this paper. The results show that under the same conditions, the higher the wax content and the solution gas?oil ratio of the formation crude, the higher bubble point pressure and the formation volume factor; when the reservoir pressure is greater than bubble point pressure, the lower the wax content and the higher the gas?oil ratio, the more significant the effect of the reservoir pressure on the formation volume factor and oil density, while the higher the wax content, the less the effect of the reservoir pressure on them. For the formation crude with high wax content, the viscosity reduction of crude oil dissolved with natural gas is obviously better than that of light oil