Combined sewage intercepting purification device

The invention provides a combined sewage intercepting purification device, which comprises a water feeding pipe, a filtering layer, a rainwater collecting tube, a back flush water pump, a back flush pipeline, an overflow weir and an intercepting well. The water feeding pipe communicates with the intercepting well, and the filtering layer is arranged in the intercepting well; the overflow weir is arranged on the position, below the filtering layer, in the intercepting well, and the filtering layer divides the intercepting well into a first area and a second area; the first area is connected with a first water discharging pipe to discharge intercepted sewage into a sewage pipe network, and the second area is connected with a second water discharging pipe to discharge clean water filtered through the filtering layer into a riverway; and the rainwater collecting tube is arranged beside the intercepting well and internally provided with the back flush water pump, and the back flush water pump and the back flush pi