Water body deep purification system and method

The invention discloses a water body deep purification system and method. The water body deep purification system comprises a pretreatment device, a coagulation device, an electrolysis denitrificationdevice, an aerobic device, a deep phosphorus removal device and a sludge treatment device. After polluted water is treated by the pretreatment device, the coagulation device, the electrolytic denitrification device, the aerobic device and the deep phosphorus removal device in sequence, 80-95% of COD in the water can be removed, and the COD of effluent is smaller than or equal to 20 mg/L; 95-99% of BOD is removed, so that the BOD of effluent is less than or equal to 4mg/L; 60-98% of total phosphorus is removed, so that the total phosphorus of effluent is less than or equal to 0.1 mg/L; 95 to 99.99% of ammonia nitrogen is removed; the ammonia nitrogen content of the effluent is less than or equal to 1.0 mg/L, and the removal rate of total nitrogen is 95-99.00%; the total nitrogen content ofthe effluent is less than