The invention relates to a method of light gasoline desulphurization by alkali washing. The method includes: (1) bringing light gasoline and an alkali solution containing sodium hydroxide into contact, mixing and performing two-phase separation so that sulfur-containing compounds in the light gasoline are extracted into the alkali solution; (2) in a supergravity reactor, mixing the extracted alkali solution to be regenerated and an oxygen-containing gas, and discharging waste gas containing disulfide and the regenerated alkali solution; (3) absorbing the disulfide in the waste gas containing the disulfide by using diesel oil; and (4) circulating the regenerated alkali solution for the extraction process of the light gasoline. The method combines and optimizes a conventional alkali liquid extraction technique, a supergravity reaction technique and a tail gas absorption technique. The regenerated alkali solution is high in quality, thus improving the desulfurization percent and reducing the discharge amount of waste alkali residue. The air waste gas absorption step reduces discharge of the sulfur-containing gas, so that the whole process meets requirements on environment protection, and a desulphurization effect that a thiol content after desulphurization is not higher than 2 ppmw is achieved.