The Pd(II)-catalyzedC–Hbond activation/C–Nbond cleavage annulation reaction of N-alkyoxyamide aryne is developed to synthesize 9,10-dihydrophenanthrenone derivatives. This reaction exhibited good functional group compatibility with yields up to 92%. Detailed mechanistic studies showed that the key to C–Nbond cleavage is the formed eight-membered palladacycle intermediate undergoing nucleophilic