With increasing concerns about global warming, and the cement plants emitting huge CO2, it is necessary to know how the CO2 emits and how much the CO2 emits due to cement manufacture in both direct and indirect ways. A precise method to calculate CO2 emissions including three processes was established in this paper and a case study was provided. From the case of LQDX plant, we can see the amount of CO2 emissions at the right level. The summary of CO2 emissions is consisted by emissions from raw materials, fuels and electricity. The direct CO2 emissions are 0.822 ton CO2 per ton clinker, and the total CO2 emissions are 0.657 ton CO2 per ton cement in this study. Therefore, the way that CO2 emissions due to cement manufacture was pictured and then measured. An approach provides a basic framework to identify various situations in different cement plants in China and other in the rest of the world. The framework would be useful in quantitatively evaluating CO2 emissions for government to know precisely CO2 emissions in cement plants.