The invention discloses a two-stage filtration type sewage treatment device which comprises a primary filter and a second filter. The primary filter comprises a primary water tank, a drive pipe, a sludge discharging assembly and a sludge discharging device. A scrubbing plate is formed on the outer wall of the lower portion of the drive pipe, and a scrubbing head is formed on the scrubbing plate. A water inlet pipe is arranged at the upper end of the second filter, and a water inlet pipe and a blow-off pipe are arranged at the lower end of the second filter. During working, a water inlet pump and a centrifugal pump are started, water undergoing primary filtration flows from a primary filtration water pipe to the second filter, a magnetic valve is turned on, water undergoing secondary filtration is discharged out of a secondary water outlet pipe, and sewage passing through a secondary filtration pipe re-flows into the primary water tank for primary filtration through a sewage pipe. Due to the design that a sludge inlet is narrow in upper portion and wide in lower portion, the sludge does not break away from a sludge discharging pipe and is finally discharged out of the sludge discharging device, and a conveying belt drives the sludge to move for a proper distance and to be discharged out of the sewage treatment system.