The effects on yield,quality and other main agronomic characters of applying sulphate-potassium magnesium to pakchoi,Tea and Watermelon through field experiments based on applying nitrogenous fertilizer and phosphate fertilizer were studed.The results showed that applying potassium fertilizer could improve yield and quality.Applying sulphate-potassium magnesium compared with applying potassium sulfate or potassium chloride,yield of pakchoi increased 3.81% and 9.88%,yield of tea increased 8.75% and 3.81%;nitrate content of pakchoi decreased 180.7mg/kg and 52.5mg/kg;Free amino acid content of tea increased 0.30% and 0.27%,polyphenol content of tea decreased 0.90% and 3.63%,caffeine content of tea increased 0.31% and 0.19%;soluble solids in the centre of watermelon increased 0.07% and 0.57%,Vc content increased 8.84% and 7.35%.Applying sulphate-potassium magnesium increased about 733 to 4041 Yuan profit than applying potassium sulfate or potassium chloride per hectare.