The invention provides a slurry circulating slag discharging system for a shaft heading machine, The system comprises a slurry inlet pipeline, a slurry discharge pipeline, a flushing pipeline, a bypass pipeline and a slurry treatment device, wherein one end of the slurry inlet pipeline is connected with the slurry treatment device, the other end of the slurry inlet pipeline is arranged in an excavation bin of the heading machine, slurry treated by the slurry treatment device is conveyed into the excavation bin, one end of the slurry discharge pipeline is arranged in the excavation bin, the other end of the slurry discharge pipeline is connected with the slurry treatment device, the slurry in the excavation bin is conveyed to the slurry treatment device through the slurry discharge pipeline, the flushing pipeline is connected with slurry discharge ports, located in the excavation bin, of the slurry inlet pipeline and the slurry discharge pipeline, the slurry discharge ports are dredgedthrough the flushing pipeline, the bypass pipeline is connected with the slurry inlet pipeline and the slurry discharge pipeline, and a slurry conveying cycle is formed between the slurry inlet pipeline, the bypass pipeline, the slurry discharge pipeline and the slurry treatment device. The slurry circulating slag discharging system integrates circulating slag discharging and slurry discharge portdredging functions, and the bypass pipeline is arranged to facilitate maintenance of the system.