The fundamental elements of national food security determine the game between the developed and developing countries, but unequal game power has led to the imbalanced rules made in Agreement on Agriculture on food security, which has severely limited the policy space of developing countries on food security. Doha negotiations on agriculture can not fundamentally change this situation. Therefore, developing countries should not rely solely on trade to achieve food security, but should adopt approaches from two aspects. First, developing countries should fight for external environment favorable for agricultural development proceeding from fair trade; Second, developing countries should strengthen domestic policy support on food production proceeding from openness and protection.