Environmental easement is non-possessory interest which imposes limitation or positive obligation on real escape. Since the late 1800s，environmental easement in the Unified Sates has developed in a considerable way. The use of conservation easements and land cruses to project undeveloped land in the Unified States has become a very popular mechanism. The US environmental easement belongs to easement in gross，public easement and agreed easement. As a mixed form of properly right，it is a better balance between economic and ecological value of the land. Hence,it becomes a flexible environmental regulation means different from"command and control"model.