A soluble concentrate of fructus isopsoraleae chalcone relates to an agricultural soluble concentrate and comprises the following raw materials in percentage by weight: 0.1-10% of fructus isopsoraleae chalcone, 8-20% of emulsifier and a solvent which is added until the concentrate reaches 100%; the pure fructus isopsoraleae chalcone or the plant extract of fructus isopsoraleae chalcone is mixed with the solvent, stirred and completely dissolved; and then the mixture is added with the emulsifier, stirred, uniformly mixed, supplemented with the solvent to reach 100%, and then kept standing for 4-5 hours. The soluble concentrate of fructus isopsoraleae chalcone is used for preventing plant fungus diseases including rice blast, apple canker, cucumber anthracnose, tomato late blight, pepper anthracnose, cucumber botrytis and rhizoctonia solani kuhn, or used for preventing plant viral diseases including tomato mosaic virus, soybean mosaic virus, tobacco mosaic virus, tobacco virus Y and potato virus Y. The soluble concentrate is well soluble with water, so that the sterilizing effect in practical application is greatly improved; and the content of fructus isopsoraleae chalcone as an effectively component is stable.