Abstract: This paper combined with the pricing policy of the Heilongjiang agricultural water and field research. The article clued from understanding the reasons for farmer irrigation behavior, and then described the negative external performance of the irrigation behavior, focusing on the substance of the negative externalities of economics. Research showed that, in the government pricing mechanism, the implementation of the existing agricultural water price was not conducive to encouraging farmers to take the initiative to save water in production. As a result, water wastage in agriculture has increased the social marginal cost of water. In the author's view, the definition of property rights was the best way for the internalization of external effects, which can achieve efficient use of water resources, and Pareto optimality by reconfiguring and operating the water resources.