The present invention relates to a 3, 4-bipyridyl pyrazole derivative, and a preparation method therefor and a medical application thereof. Specifically, the present invention relates to a new 3, 4-bipyridyl pyrazole derivative as shown in formula (I), a preparation method for the derivative, a pharmaceutical composition containing the derivative, a use of the derivative as a therapeutic agent, in particular as a TGF-β inhibitor, and a use of the derivative in the preparation of a drug which treats, prevents or reduces cancer mediated by TGF-β overexpression. The substituents in formula (I) have the same definitions as in the description.