The invention relates to a method for improving octane value of gasoline, mainly for solving the problem how to convert inferior gasoline rich in olefin into high-quality gasoline rich in arene, which is not related in the prior art. According to the method, inferior gasoline and benzene are taken as raw materials, crystal silicon aluminate is taken as the catalyst, olefin in the gasoline is converted into alkyl benzene in a fixed bed reactor, the fixed bed reactor has at least two sections of beds, each section of the bed is loaded with the catalyst, benzene is added into the reactor completely or section by section, the inferior gasoline is added into the reactor section by section, wherein at least a part of the product at the secondary section of the catalyst bed externally circulates to the first section of bed of the reactor; and after the other part of the product is separated by a light component removing tower, a benzene tower and a gasoline refining tower, the material flow at the top of the gasoline refining tower, the material flow at the top of the light component removing tower and the material flow at the top of the benzene tower are blended so as to obtain the gasoline with high octane value. The technical scheme well solves the problem and the method can be used in industrial production of improving the octane value of the gasoline.