The invention discloses a washing system for a sanitary wastewater pipe of an airplane. The washing system is connected with the sanitary wastewater pipe of the airplane through an external connection pipe to form a circulation loop so that a wastewater pipe cleaning agent can be circulated in the wastewater pipe under the effect of pressure, and the effect of washing the wastewater pipe of the airplane with a disincrustant can be achieved. The system can work by adopting a negative pressure principle and can also work by adopting a positive pressure principle, circulated cleaning is achieved, the cleaning effect is good, and efficiency is high. The system is suitable for various airplane types operating at present, manual participation is not needed in the overall system running process, the running time is short, and safety is high.