We have investigated the domain growth of antiferroelectric liquid crystal display under the switching process by means of CCD camera pictures. Its dynamic behavior was simulated by our extended bilayer model. In this model, we supplement free energy of antiferroelectric liquid crystal display with the coupling coefficient between adjacent molecules in the same layer, because domain growth propagates parallel to the smectic layer. The mechanism of the domain growth in antiferroelectric liquid crystal display can be described by the extended bilayer model.