Pot experiment was conducted to study the effects of nitrogen and potassium on the yield, quality and physiology indices of garden sass. The results indicated that the yield, nitrate content of plant and chlorophyll concentration of leaf were increased with increase of nitrogen application rate at the range of 0-0.32 g/kg, but the soluble sugar content was significantly decreased at the same time. The available photosynthesis rate of leaf and free amino acid content of plant were gradually increased at the range of application rate of 0-0.16 g/kg and then gradually decreased at the range of application rate of 0.16-0.32 g/kg. Under the experiment condition and with nitrogen application rate of 0.24-0.32 g/kg , applying potassium has specified roles on increasing yield, improving quality as well as decreasing nitrate content.