In this paper, by using the non-linear effects and also destructive and constructive interferences between waveguides, we have designed and simulated an all-optical full-Subtractor based on two-dimensional photonic crystals. The proposed Subtractor has a very simple structure which is composed of 33×31 silicon rods immersed in air in a square lattice and involves three input ports (bits) and an additional waveguide to exhaust the unwanted light. We imposed some defect rods to control the behavior of the light. The used non-linear material, is a doped glass with 1.4×10 − 14 m 2 /w non-linear refractive index which is very greater than the non-linearity refractive index of silicon, 3.46×10 − 20 m 2 /w. Since the proposed structure is very simple and compact, it can be applicable in optical integrated circuits and optical calculations.