This invention relates to an additive capable of increasing the gasoline octane (by 2-3 units) with minimum loss of gasoline. More specifically, the present invention discloses a fluid catalytic cracking additive composition capable of enhancing gasoline octane, said composition comprising 5-50 wt. % zeolite component, 0-15 wt % alumina, 5-20 wt % colloidal silica, 10-60 wt % kaolin clay, 5-15 wt % phosphate, and 0.1 to 5.0 wt. % of bivalent metal selected from Group-IIA or Group-IB, wherein the zeolite component comprises of medium pore pentasil zeolite in an amount of 1 to 50 wt. % and said zeolite consists of one or more MFI topology zeolite having SiO2/Al2O3 mole ratio in the range of 10-280. The present invention also discloses a process for preparation of the additive.