The invention discloses an accumulated mud clearing device of a main brush box body of a street sweeper. The accumulated mud clearing device comprises scrapers, a guide mechanism and a mud scraping control mechanism, wherein the scrapers are movably arranged and used for clearing accumulated mud on a front baffle of the main brush box body; the guide mechanism is arranged on the front baffle and used for guiding the scrapers; and the mud scraping control mechanism is connected with the scrapers and used for controlling the scrapers to move in the length direction of the front baffle; and the scrapers are located between the front baffle and a main brush. According to the accumulated mud clearing device of the main brush box body of the street sweeper, the structure is simple, operation is convenient, the accumulated mud attached to the front baffle of the main brush box body can be rapidly cleared, thus it is guaranteed that the main brush can work normally, the failure rate is decreased, damage to transmission systems such as a main brush motor is reduced, the situation that the sweeping effect is affected by abrasion deformation of the main brush is relieved, and the customer using cost and the after-sale cost are reduced.