The invention discloses a self-flushing anti-blocking waste water jar. The self-flushing anti-blocking waste water jar comprises a shell and a shell cap arranged at the lower end of the shell, whereinthe upper end of the shell is provided with a water outlet end, and the lower end of the shell cap is provided with a water inlet end. The shell is internally provided with an inner pipe barrel, a lower plug, an upper plug, a first spring and a second spring, wherein a piston is arranged in the inner pipe barrel, and the piston is provided with a vertically-through first through hole; the lower plug is arranged at the lower end of the inner pipe barrel, a vertically-through second through hole is formed in the lower plug, and water flows out of the second through hole to push the piston to move upwards; the upper plug is arranged at the upper end of the inner pipe barrel and is provided with a vertically-through third through hole; the first spring is contained in the inner pipe barrel and is clamped between the upper plug and the piston; the second spring is pressed on the top end of the upper plug; the bottom of the upper plug is provided with a blocking needle, and the first through hole is used for allowing the blocking needle to be inserted in; and the upper plug is also provided with a thimble used for blocking the piston. A waste water discharging device of a pure mechanical structure is adopted, no circuit system is needed, and good self-control and anti-blocking characteristics are achieved.