Renewable power-to-ammonia (ReP2A) production based on green hydrogen is a critical approach to de-carbonizing the energy and chemical sectors. Green ammonia production is naturally impacted by the uncertainty of renewable energy, posing profit risks for ammonia market participants. To address this issue, this study proposes the concept of green ammonia futures as a financial tool to provide risk aversion. Firstly, inspired by the concepts of the new energy futures and the traditional commodity futures, we propose two modes of green ammonia futures and establish their general equilibrium models. The equilibrium prices and positions are then deduced. A case study based on a ReP2A demo project under construction in Inner Mongolia Autonomous Region, China quantifies the impact of green ammonia futures on the profits and risks of the ammonia market participants. The result shows that the new energy-style green ammonia futures raises the utilities of both the seller and buyer; the traditional commodity-style one fails to do so. Impacting factors such as risk aversion attitude or energy-to-ammonia conversion efficiency are also analyzed.