A²/O-Biological contact oxidation processes——flocculation and coagulation settling——sand filter processes wasused to trea the wastewater at the piggery. The treated wastewater have been recycled and reuse with special pipe for washingin the piggery. The raw wastewater flow through the screen tank, primary sediment tank, biogas tank, anoxic tank, aerationtank, secondary sediment tank, biological contact oxidation tank, chemical reaction tank, denitrogen tank, and sands filter.The sludge flowed to the dewatering square for desiccation. The effuent water from the system achieve and over the Second Class Drainage Standard according to "The National Standard of Wastewater Overall Drainage (GB8978-88)" and reuses for washing piggery excrements directly.