Abstract: According to the reservoir geological conditions and fluid characteristics of Gao3624 block in Gaosheng oilfield, combined with the mechanism of supercritical steam stimulation, the numerical model of pressure drop and temperature drop in supercritical steam drive is established by solving the governing equations such as momentum equation, energy equation and heat dissipation equation. The numerical distribution of supercritical steam parameters in gas injection well is calculated, and the variation of thermodynamic parameters, pressure drop and casing temperature in the process of supercritical steam huff and puff in vertical wellbore is studied. On the basis of computational fluid dynamics, by changing the simulation conditions such as injection steam pressure and steam temperature, the distribution of the temperature field and pressure field at different positions are obtained, which further deepens the research on the phase change law of supercritical steam, and provides the basis for the optimization of supercritical steam injection parameters and the enhancement of deep heavy oil recovery in Gaosheng oilfield.