The present invention provides a substituted fused heteroaryl compound serving as a kinase inhibitor, and applications thereof. Specifically, the present invention provides a compound represented by formula I, or a medicinal salt or a prodrug thereof, A1-A4, B1-B3, D1-D4 and R1-R3 being defined herein. The compound represented by formula I is a kinase inhibitor. Accordingly, the compound in the present invention can be used for treating cancer and other clinical conditions caused by a defect in a DDR function.