The utility model relates to a light oil tank circulation slag flushing device. A circulation slag flushing branch is connected to the exterior of a light oil tank feeding pipeline. The circulation slag flushing branch comprises a first circulation slag flushing pump, a benzene slag precipitation tank and a second circulation slag flushing pump which are connected together in series through pipelines. An inlet of the first circulation slag flushing pump is communicated with the light oil tank feeding pipeline. The benzene slag precipitation tank is a horizontal sealing tank. A slag baffle is longitudinally arranged inside the benzene precipitation tank. The region inside the benzene slag precipitation tank is partitioned into a benzene slag precipitation region and a clarification oil region through the slag baffle. A benzene slag outlet is connected with a benzene slag pipeline which is communicated with the pipeline between the first circulation slag flushing pump and the light oil tank feeding pipeline. The light oil tank circulation slag flushing device is simple in structure, convenient to transform, assemble and operate and capable of conducting storage tank circulation slag flushing cleaning regularly, reducing benzene slag accumulated inside the storage tank, prolonging the continuous service life of the storage tank, and ensuring stable operation of a subsequent processing system.