During the exploration and exploitation of high-temperature and high-pressure acid gas reservoirs in the Yinggehai Basin, the acid gas CO2 in the formation can rapidly dissolve in the drilling fluid and react with it. This leads to a significant deviation between the detected amount of CO2 content in gas logging and the actual CO2 content in the formation, complicating the accurate assessment of the formation's CO2 content. By experimentally simulating the underground wellbore environment of drilling operations, and based on the reaction characteristics of CO2 with drilling fluid under the high-temperature and high-pressure conditions, we analyzed the relationship between pH value, temperature, pressure, calcium and magnesium ions, carbonate, bicarbonate and their respective changes and the CO2 occurrence content. Using multiple regression analysis, we analyzed the pattern of parameter changes influenced by the interaction of CO2 with the drilling fluid and developed a prediction model for CO2 occurrence content in drilling fluid system based on the change of ion concentration, deriving 14 prediction equations. The results show that the three-parameter equation is the most convenient for field application. The five-parameter equation provides a good explanation for the adsorption behavior of clay components in drilling fluid towards CO2 under high pressure. Averaging the prediction results from multi-parameter equation results in a deviation of less than 30%. The research results can provide technical reference for accurate prediction of CO2 content in formations during the drilling of high-temperature and high-pressure wells with high alkaline mud.