Abstract: The legal recognition of the basic principles of environmental law reflects two main functions, one is the structurization of environmental law, and the second is the legitimating of environmental policy. Precaution, as a legal principle, originated in Germany in the eighties of the 20th century. The initial core of the principle is that the society should seek to avoid damage to the environment through careful advance planning and prevention of potentially harmful behaviors. The precautionary principle needs to meet two conditions: first, the lack of certainty; second, the existence of a serious risk of irreversible harm. Currently, there are two versions of the precautionary principle as“strong” and“weak” in the world, yet to come to a unified understanding in the concept context. The core of the implementation of precautionary principle in domestic legislation is the question of cost-effectiveness, which will also be a major obstacle to its localization in China environmental legislation in the present stage.