In order to realize the ultrastrong absorption of graphene with electrical modulation properties, we designed a composite structure of graphene and parity-time (PT) symmetry photonic crystal, which is achieved by placing the graphene layer on the top layer of the PT symmetry photonic crystal. In this paper, the absorption properties of graphene and the electrical modulating properties of the structure were theoretically analyzed based on the transfer matrix method. The result shows that the proposed structure can achieve the absorption of 31.5 dB for the communication wavelength of 1550 nm; meanwhile, by setting the electric field intensity to ±0.02V/nm, the absorption of graphene can be largely modulated to realize an electrically switchable effect, the modulation depth of graphene absorption can reach nearly 100%, and the operation speed is also close to 8.171 GHz. This investigation provides a novel approach to design graphene-based optoelectronic devices and optical communication devices.