Based on the basic theories of thermal economics and thermal engineering, a magnesia factory in Liaoning Province was chosen as a research object. Researchers construct the production flow structure of different fused magnesia processes and establish mathematical models that consider calculating exergy income, exergy cost, exergy transfer, and carbon emission. The changes in the system economy and environmental protection of different production processes are analyzed through calculation. The results show that the cleaner fused magnesia system has unique advantages in exergy economic income and carbon emission.