The design and performance of a commercial hybrid solar gas turbine are investigated in this paper. To provide a complete study, an in-house Matlab code is used to estimate the geometric design parameters of the solar receiver and the tower. SolarPILOT software is used to layout and estimate the performance of the heliostat field. TRNSYS software is used to simulate the performance of the complete system. An exsiting fossil gas turbine of 160MW located at Awbari, Libya is selected as a case study. It is supposted to be modified into hybrid solar gas turbine of nominal solar share of 30%. Results show that the annual optical efficiency of the heliostat field is 65%. The nominal thermal efficiency the hybrid solar gas turbine is 25%.