The present disclosure belongs to the field of medicinal chemistry, and relates to a novel pyridone derivative represented by Formula (I) or a stereoisomer, a pharmaceutically acceptable salt, a solvate or a crystal thereof, and use thereof in the preparation of a drug for preventing or treating diseases such as influenza type A viral infection and/or influenza type B viral infection, particularly use thereof as a PA subunit cap-dependent endonuclease inhibitor for preventing or treating diseases such as influenza type A viral infection and/or influenza type B viral infection. The compounds of the present disclosure have significant activity in inhibiting influenza endonuclease and influenza DNA, can be used either alone or in combination with a neuraminidase inhibitor, a nucleoside drug, a PB2 inhibitor, a PB1 inhibitor, an M2 inhibitor or other anti-influenza drugs, significantly shorten the time of influenza infection and reduces mortality, and have excellent clinical application prospects.