A chassis foam sprayer comprises a bottom plate, a solvent pot and a flushing pipe arranged above the bottom plate, rollers arranged below the bottom plate, and an upper cover covering above the bottom plate, wherein one end of the flushing pipe is provided with a water inlet connector which can be externally connected with a high-pressure water gun, the other end of the flushing pipe is provided with at least one nozzle, and a connecting pipe is arranged between the solvent pot and the flushing pipe; the high-pressure water gun is fixedly connected with the water inlet connector by arranging the rollers on the bottom plate, and then the foam sprayer is pushed in at the position of the chassis of the automobile, so that the position can be conveniently moved, and all positions of the chassis can be conveniently cleaned; moreover, the solvent pot is equipped with car wash liquid, so that the chassis can be subjected to foam spraying first, and then washed with clean water for thorough cleaning.