Abstract: The route towards sustainable development is much more controversial than the goal itself. Too often, people with different cognition and values cannot achieve consensus on "what the problem is" and "what should be done" in pursuit of a better sustainable development model. By using the debate on farmland red line in China as a typical example, this paper attempts to demonstrate how policy discourse competes with each other at different levels and how they shape people's thinking. In this case, either land-control discourse or land-utilized discourse has its own evidence, interpretations and epistemic figures that resist from the opponent's argument. The paper finally emphasizes the importance of democratic deliberation, which may play a crucial role in challenging discursive hegemony, creating arenas for communication and facilitating consensus building to realize effective environmental governance and sustainable development.