In this study, structural, optical, electronic, thermodynamic, dynamic and elasticproperties of Ga1-xAlxN alloys have been investigated using the combination of ab initio method based on Density Functional Theory (DFT). Generalized Gradient Approximation (GGA) has been used as exchange correlation. Components ofelastic constants have been used in order to calculate Poisson Ratio, Bulk Modulus, Shear Modulus, Compressibility, Kleiman Parameter, CouchyPressure. Refractive Constants, Extinction Coefficient, Absorption Coefficient, Energy Loss Function and Conductance Values have been obtained from dielectric constants using Kramers-Kronig relations. The properties of ternary alloys have been obtained with reference to known characteristics of binary alloys. The alloys have semiconductor properties with direct band transmission whose band gaps was determined as 2.19, 2.62 and 3.43 eV while Al contents were x = 0.25, x = 0.5 and x = 0.75respectively. They form cubic structure with 3 elastic constants for x = 0.75 and 0.25, and tetragonal structure with 6 elastic constants for x = 0.50. Ga0.5Al0.5N and Ga0.75Al0.25N alloys are elastic whereas Ga0.25Al0.75N is brittle. Compressibility varies depending on increasing x where its maximum is 0.0053 1 /GPa, at x = 0.25. Real parts of Refraction Constants and Dielectric Constants graphs have been found to be have similar trend. Characteristic peak of Lose Function is 19.84 eV for x = 0.75 that is the highest Plasmon Frequency. When Al amount increases, the distance between the maximum and minimum points in the phonon dispersion curves increases so the conductivity decreases. Finally, alloys with large band gaps are suitable semiconductors for optoelectronic devices such as diodes and laser.