Carbon trading mechanism is a system to regulate the international carbon trading market. Carbon assets are not commodities in the first place and have no significant development value. However, the signing of 1997 Kyoto Protocol changed all this. According to the Kyoto Protocol, by 20 10, the amount of six greenhouse gases such as carbon dioxide and methane emitted by all developed countries will be reduced by 5.2% compared with 1990.

However, due to the high efficiency of energy utilization and the optimization of energy structure in developed countries, new energy technologies are widely adopted, and further emission reduction in China is costly and difficult. However, developing countries have low energy efficiency, large space for emission reduction and low cost.

Pigou theory refers to taxing polluters according to the degree of harm caused by pollution, and using taxes to make up the gap between private costs and social costs of polluters' production and make them equal. It was first put forward by the British economist Arthur Cecil (1877- 1959). This kind of tax is called Pigou tax.

Environmental tax can be traced back to Pigouivaintax proposed by Pigou, a welfare economist. Pigou tax is a classic textbook way to solve environmental problems and belongs to direct tax.

It is based on the discharge of pollutants or the harm of economic activities to determine the tax obligation, so it is a specific tax. The unit tax amount of Pigou tax should be determined according to the equilibrium point that the marginal social cost of an economic activity is equal to the marginal income, when the tax rate of sewage discharge is at the best level.