The crystal structure， electron density difference, electronic properties, optical properties and thermodynamic property of AlxGa1-x As system were calculated by the first principle method on the density functional theory as aluminum composition x changes from 0 to 1. The results show that, the lattice constant of AlxGa1-xAs system increases linearly with composition x of aluminum. The band structure shows that, the energy gap width increases with the increase of aluminum composition, and when x≥0.5, the energy gap will change from direct one to indirect one. The coefficient of static dielectric loss ε1(0) decrease with the increase of aluminum, and the band edge of the absorption coefficient has blue shifts with the increase of x. It can be seen from the variation of Debye temperature of the material system with the aluminum composition that when aluminum composition increases, the sound velocity and elastic stiffness constants of the system also increase correspondingly. At high temperature, the nonlinear increase of the specific heat capacity is caused by the nonlinear increase of the original cell number of AlxGa1-xAs per unit mass. By analyzing the photoelectric characteristics and thermodynamic property of AlxGa1-x As system with different aluminum atomic composition, the theoretical foundation is laid for the application of AlxGa1-x As semiconductor materials in optoelectronic devices, integrated circuits solar cells and other aspects as well as the subsequent in-depth research.