The United States and China jointly issued "Joint Statement on Climate Change"on September 25,2015. According to the statement, China will launch the national carbon emissions trading scheme (ETS) in 2017 while the accurate counting of carbon emissions is essential to China's ETS. In order to make enterprises understand the status of their own carbon emissions,broaden their knowledge reserves in the field of carbon emissions, and master the power industry carbon emissions calculation method, a power plant in Inner Mongolia is taken as an example to illustrate the process of data collection and calculation of carbon emissions in details. The fuel activity levels, fuel emissions factor and carbon emissions, etc. are obtained through calculation. The relationship between CO_2 emissions and power supply are studied quantitatively to evaluate the power plant's carbon emissions.