Perturbed Chain-Statistical Associating Fluid Theory (PC-SAFT) equation of state (EoS) can be applied to predict the physical properties of CO₂-based mixtures in the CO₂ power cycle. The convergence of PC-SAFT EoS is poor when calculating vapor-liquid equilibrium (VLE) of CO₂-based mixtures. In this paper, the vapor pressure estimation method based on group contribution is used to provide the initial value for the PC-SAFT EoS and complete the calculation of the VLE of CO₂-based mixtures from the perspective of groups. The accuracy of this method is higher than that of REFPROP 9.0 in many cases, especially in the case of a high CO₂ ratio. For the calculation of CO₂-based mixtures with large temperature slips, this method will not calculate the uneven cusps in REFPROP 9.0. It avoids abnormal calculation results in some cases and is a stable and reliable calculation method.