The present invention relates to a five-membered heteroaryl ring bridged ring derivative, a preparation method therefor and the medical use thereof. In particular, the present invention relates to a new five-membered heteroaryl ring bridged ring derivative as shown in formula (I), a preparation method therefor and a pharmaceutical composition comprising the derivative, and the use thereof as a therapeutic agent, in particular as a TGF-β inhibitor, and the use in the preparation of a drug for treating, preventing or reducing cancers mediated by the over-expression of TGF-β, wherein the definition of each substituent in the general formula (I) is the same as defined in the description.