The present invention relates to formylpyridine derivatives having FGFR4 inhibitory activities, a preparation method therefor and use thereof, the formylpyridine derivatives having a structure of formula (I), the definition of each substituent in the formula being as described in the description and claims. The series of compounds of the present invention have very strong inhibitory effects on FGFR4 kinases, have very high selectivity, and can be widely used in the preparation of medicaments for treating cancers, particularly prostate cancer, liver cancer, pancreatic cancer, esophageal cancer, stomach cancer, lung cancer, breast cancer, ovarian cancer, colon cancer, skin cancer, neuroglioblastoma or rhabdomyosarcoma, and prospectively will be further developed to become a new generation of FGFR4 inhibitors.