All-optical logic devices are essential for realizing all-optical signal processing. A full-adder is the basic building block of an arithmetic logic unit used in all-optical signal processing systems. In this paper, we aim to design an ultrafast and compact all-optical full-adder based on the photonic crystal. In this structure, three main inputs are connected to the three waveguides. Also, we have added one input waveguide to create symmetry in the structure and to improve the performance of the device. A linear point defect and two nonlinear rods of doped glass and chalcogenide are used to control the light behavior. The designed structure consists of 21×21 dielectric rods with a radius of 114 nm in a square cell and a lattice constant of 543.3 nm. Also, the area of the proposed structure is 130µm 2, and the maximum delay time of the proposed structure is about 1 ps, which indicates the minimum data rate of 1 THz. The maximum normalized power for low states and the minimum normalized power for high states are obtained as 25% and 75%, respectively. These characteristics make the proposed full-adder appropriate for high-speed data processing systems.