A series of novel 6-cinnamoyl-2H-benzo[b][1,4]oxazin-3(4H)-one derivatives was synthesized. The structures of compounds were characterized by (1)H NMR, IR, and MS. Moreover, representative crystal structure was determined by X-ray diffraction analysis. The preliminary biological evaluation of all these compounds showed that compounds 3a-3d would suppress the growth of A549 lung cells effectively by inducing autophagy and cell cycle arrest.