The utility model relates to a dephosphorizing and denitrifying granular sludge bioreactor used for the biological phosphorus and nitrogen removal process in sewage treatment. The bioreactor comprises multi-stage partition plates arranged inside a biological reaction tank in a staggered manner and dividing the biological reaction tank into an oxygen-free zone, an anaerobic zone and an aerobic zone; a plurality of meshed plates are arranged on the water-carrying cross sections of the oxygen-free zone, the anaerobic zone and the aerobic zone, the oxygen-free zone, the anaerobic zone and the aerobic zone are distributed in sequence from the sewage inflow end to the sewage outflow end of the biological reaction tank; a secondary settlement tank is connected behind the aerobic zone; the oxygen-free zone and the anaerobic zone are divided into five compartments respectively; the aerobic zone is divided into five compartments; a sewage distributing pipe is connected with a first oxygen-free zone, a first anaerobic zone and a first aerobic zone; and the returned activated sludge of the secondary settlement tank is connected with the first oxygen-free zone through a sludge return pipe. The dephosphorizing and denitrifying granular sludge bioreactor adopts the meshed plates to change the flow environment and the condensation condition and promote the production of the aerobic or the anaerobic granular sludge inside the reactor, thereby greatly improving the biochemical reactions for phosphorus and nitrogen removal. Besides, the efficiency of the biological reaction is increased by more than 20% and the emission of phosphorus and nitrogen pollutants in the sewage meets the standard.