In the context of low-carbon economy, the assumption of free carbon emission is disappearing, and manufacturing enterprises need to plan their low-carbon strategies. Enterprises need to consider a series of issues such as investment in low-carbon technology, control and prevention of carbon emissions in the production process, and trading of carbon emission rights. These decisions and actions require accounting to reflect enterprises' carbon emission activities. This paper starts with the connotation of carbon emission cost, analyzes the confirmation process and classification of carbon emission cost, and obtains the combination point of optimal carbon emission and carbon emission cost by constructing the short-term carbon emission cost decision model. After further analysis of the long-term carbon emission cost decision model, it is proposed that the long-term carbon emission cost will decrease with the decrease of carbon emission. At the same time, the paper takes the automobile industry as an example to analyze the carbon tax levied on "carbon emission", and verifies the decision-making model of short-term and long-term carbon emission cost.