Ultra-deep formations exhibit high-temperature and high-pressure conditions, with extended wellbores characterized by significant wellhead-to-bottomhole temperature and pressure differentials, leading to complex fluid phase behavior mechanisms during drilling. Phase-state prediction is critical for accurate fluid property characterization. To address the multicomponent flow dynamics involving gas, liquid, supercritical phases, and drilling fluids in ultra-deep wellbores, a multicomponent multiphase equilibrium model was developed. Phase behavior experiments and model validation were conducted using representative fluid compositions from ultra-deep wells in the Tarim YH Block, achieving a model accuracy of 97.71%. The spatiotemporal evolution law of multi-component fluid phase states in ultra deep well drilling wellbore was analyzed. The results show that there is no gas-liquid two-phase zone in the dry gas within the temperature and pressure range of the wellbore, and it only flows in the form of gas phase. Moisture, high carbon dioxide gas, and condensate gas exist in four states at different locations in the wellbore: gaseous, liquid, gas-liquid two-phase, and supercritical. The increase in wellbore pressure gradient, geothermal gradient, and drilling fluid displacement brings the phase transition point closer to the wellhead, with the pressure gradient having a greater impact. The direct reason for the strong concealment of gas invasion is the decrease in density after the gas breaks through the phase transition point. The calculation results of the example well show that the research method improves the accuracy of wellbore pressure calculation in ultra deep drilling by 2.81%, which can provide theoretical support for the safety of ultra deep drilling.