Oil-based drilling fluid is mainly used for horizontal sections drilling of shale gas horizontal well in China. Due to the expensive cost of cutting treatment, it is urgent to develop and apply a high performance water-based drilling fluid system with environmental protection characteristics. By the laboratory experiments, main treatment agents of plugging agent and filtration-reducing agent were optimizingly selected, and the formula of potassium ammonium chloride based film-forming drilling fluid system was developed with evaluation experiments on temperature resistance, lubrication, anti-collapse and inhibition, plugging and anti-pollution properties. The experimental results show that this drilling fluid has good rheology with excellent temperature resistance up to 150℃, it is also featured by good lubrication performance, strong resistance to salt and calcium pollution, leakage proof and plugging as well as strong anti-collapse and inhibition.