The invention discloses an electrophoresis paint-spraying pretreatment device for surfaces of mechanical parts and fittings. The electrophoresis paint-spraying pretreatment device comprises a housingI, wherein an inner cavity of the housing I is hollow; the bottom wall of the housing I is sequentially connected with a motor I, a motor II and a motor III in the horizontal direction; one end of themotor I, one end of the motor II and one end of the motor III are separately connected with a rotary shaft I, a rotary shaft II and a rotary shaft III; the top of the housing I is sequentially connected with a conveyor belt I, a controller, a frame body, a water tank, a barrel body, a supporting rod, a booster pump, a housing II, an electrophoresis slot and a conveyor belt II in the horizontal direction; one end, away from the housing I, of the conveyor belt I is fixedly connected with a placing plate; the placing plate is positioned on the top of the water tank; and the side wall of one side, away from the conveyor belt, of the water tank is sequentially connected with a water pump and a water introducing tube in the vertical direction. The electrophoresis paint-spraying pretreatment device is simple in structure, is convenient to operate, realizes pretreatment for electrophoresis parts and fittings and a treatment function after electrophoresis is completed, and improves electrophoresis quality.