An azatricyclic compound (as represented by Formula I) which acts as an inhibitor of fibroblast growth factor receptors (FGFR), as well as a pharmaceutical composition thereof, a preparation method, and a use therefor in the treatment of FGFR-mediated diseases are provided. The azatricyclic compound exerts an effect by means of participating in the regulation of a plurality of processes such as cell proliferation, apoptosis, migration, neovascularization, and the like.