Based on the plane-wave ultra-soft pseudo-potential in the first-principles of density functional theory and by using the generalized gradient approximation and the Heyd-Scuseria-Ernzerhof 03 (HSE03) method to correct the energy bands and density of states, the crystal structure, the electronic structure and the optical property of AlN1-xPx (x=0, 0.25, 0.50, 0.75, 1) alloys are studied. The results show that the lattice constant of AlN1-xPx alloys increases linearly as the P component increases. AlN1-xPx (x=0, 0.25, 0.75, 1) alloys are of the cubic system, while AlN0.50P0.50 alloy belongs to the tetragonal system. The band gap of AlN1-xPx alloys firstly decreases and then increases as the P component increases. AlN and AlP alloys are the indirect band gap semiconductors, while AlN1-xPx (x=0.25, 0.50, 0.75) alloys belong to the direct band gap semiconductors. The presence of P destroys the original eigenvalues and the degenerate states of AlN, and changes the electronic band structures. As the P component increases, the optical characteristic curves of AlN1-xPx move towards the low energy region, and the subsidiary strong peaks of the imaginary parts of dielectric functions gradually fade away. AlN1-xPx alloys can absorb the ultraviolet light strongly and the presence of P can broaden the absorption region of visible light.