The invention relates to a sewage treatment device, in particular relates to a multistage recirculation reactor for anaerobic sludge. The whole reactor is divided into a precipitation zone, an upper reaction zone, a middle reaction zone and a lower reaction zone through an upper three-phase separator, a middle three-phase separator and a lower gas collector which are successively arranged inside the reactor from up to down; the bottom of a gas-liquid separation tank is connected with an inner reflux circulation pipe which stretches to the bottom inside the reactor; the bottom inside the reactor is provided with an inner reflux liquid guiedvane and a water distribution pipe, wherein the inner reflux liquid guiedvane is corresponding to the outlet of the inner reflux circulation pipe, the effluent direction is tangent to the inner reflux liquid guiedvane, and the water distribution pipe is connected with a water inlet pipe II; the lower parts of the upper reaction zone and the middle reaction zone are respectively provided with an external duct; and the outside of the reactor is provided with an outer reflux circulation pipe which is respectively connected with a water outlet pipe, a water inlet pipe I and the external duct. By using the reactor, the external flow of sludge can be effectively prevented, and the sludge can be effectively mixed by utilizing inner and outer double steam guidance systems and the water distribution device.