The invention discloses an automatic sewage draining and cleaning device for a RV withdrawable black water tank. The automatic sewage draining and cleaning device comprises a cleaning supply pile, a sewage suction device and a cleaning gun, wherein the cleaning supply pile comprises a pile body, a faucet, a charging port, a flushing port, a sewage draining exit, a self-priming sewage pump, a billing device, a cleaning gun connection port, a first electronically controlled ball valve, a second electronically controlled ball valve, a fixed clamping groove and a hook; and the sewage suction device comprises a water inlet hose, a sewage draining hose, and a connection end cover, a support ball, a sewage suction head, a fixed snap ring, and a plurality of limit snap rings. The automatic sewagedraining and cleaning device uses a mechanical method to dump sewage in the black water tank, saves manpower, and is suitable for RV camps and service areas of expressways, so as to create a more comfortable and environmentally friendly driving experience for RV drivers and passengers.