The present paper presents electronic structure and optical properties of the Ga x As x clusters for x= 10,13,15,18, 20, 25 and 30 using density functional theory (DFT) method. The Ga-Ga bond length lies in range of 2.50-2.69 A 0 , the As-As bond length lies in range 2.58-2.62 A 0 and Ga-As bonds length is in range 2.46-2.52 A 0 . The variation of polarizability, which reflects optical activity, with increase cluster size is presented and the study suggests that Ga25As25 cluster has more optical activity in comparison with other studied clusters.