The invention discloses a device for characterizing the soot fragmentation characteristic of diesel engine exhaust based on a depolarization ratio. The device comprises a combustor, a displacement table, a stainless steel probe sampling system, a Raman spectrometer, a gas chromatograph, an exhaust collecting device and a computer control system. The combustor includes a main cylindrical body; a cellular plunger is embedded into the upper end of the body and is formed by a plurality of long steel tubes; a gas inlet of the combustor is connected with all gas bottles and a diesel engine exhaust manifold by pipelines; and the exhaust manifold is connected to the gas chromatograph and the exhaust collecting device through branch pipes. A vacuum pump absorbs soot to a filter film arranged in a sampling device by a suction force; and the soot on the filter film is used for the Raman spectrometer analysis. The computer control system is connected with the gas chromatograph, the Raman spectrometer, a flow meter and the displacement table. According to the invention, the analysis of the fragmentation characteristic of the soot particle of the diesel engine exhaust under the conditions of lean burning and rich combustion is realized; and the influence on the fragmentation characteristic of the soot in the diesel engine exhaust by the fuel-air equivalence ratio is obtained.