Graphdiyne (GD) is one of carbon allotropes with the unique structure and has ideal high strength, excellent light transmittance, electrical conductivity, high carrier mobility, and thermal conductivity. GD with a natural band gap is an intrinsic semiconductor with special charge transport properties. GD shows a band gap in the range of 0.45 to 1.30 eV, compared with graphene without band gap, which has a promising potential for electronic, catalytic, optical and mechanical applications. Also, GD has two different Dirac cones near the top and bottom of the Fermi energy level, indicating that GD is a self-doped semiconductor with charge carriers and does not require additional doping like graphene. GD can be used as a potential and excellent photocatalytic material, and theoretically it is needed to be modified to build active sites for efficient photo-induced reactions.