In 2004, Tuojiang River water pollution has typical external negative effect. According to economic principle that social marginal revenue of pollution control, for example, continuous increase of asset and health of people, is equal to social marginal cost of pollution control. Eliminating external effect and maximizing social efficiency is the important role of government in market economy. The play of this role must depend on a series of responsibilities and behaviors such as proper public commodity, macro - economy adjustment, reasonable redistribution of revenue and asset, protection of market order and so on.