The invention discloses a phagocytosing type bacterium. The phagocytosing type bacterium is identified to be a bdellovibrio organism, called bdellovibrio for short and classified and named as Bdellovibrio sp., the strain is preserved in the China General Microbiological Culture Collection Center on May 12th, 2016, and the preservation serial number is CGMCC No.11671. The invention further discloses application of the phagocytosing type bacterium in reducing sludge, and further discloses a bacterium extract. The strain is obtained through screening in sludge of a secondary sedimentation tank of a municipal wastewater treatment plant and meets the biosafety regulations; the strain serves as the phagocytosing type bacterium to be applied in sludge cell disruption dewatering, and the sludge dewatering and reducing performance is greatly improved by phagocytosing suspension bacteria and splitting sludge flocs, so that the operation cost of the wastewater treatment plant is reduced, both ecological safety and sanitary safety are considered, and the ecological civilization construction of the environment is promoted.