Disclosed is an isoquinolinone compound as shown in Formula (I) or a stereoisomer, pharmaceutically acceptable salt, solvate or crystal thereof, and a preparation method thereof, and use thereof in the preparation of drugs for treating or preventing viral infectious diseases caused by the hepatitis B virus (HBV) and other viruses, in particular, use thereof in drugs as HBV surface antigen inhibitors and HBV DNA production inhibitors. The compound has a significant activity in inhibiting hepatitis B surface antigen and hepatitis B DNA, and is possible to significantly improve the probability of curing hepatitis B by administration in combination with nucleoside drugs or other drugs in the future, and has good clinical application prospects.
