The invention discloses a hydraulic dismantling device and is applicable to the technical field of petroleum drilling. The hydraulic dismantling device comprises a fixing sleeve and a main body. The fixing sleeve is used for being connected with the cup edge of a pulp cup to be dismantled. The fixing sleeve is internally provided with a hollow channel. The end of the main body is fixed to the interior of the hollow channel of the fixing sleeve. The main body comprises a hydraulic mechanism, an operation end and an extension end, wherein the operation end and the extension end are arranged at the two ends of the hydraulic mechanism correspondingly. The operation end is used for controlling hydraulic oil to flow to a piston end face of the extension end to enable the extension end to extendout. Through the hydraulic dismantling device, the problem existing in dismantling a pulp cup in the prior art can be effectively solved, and it can be guaranteed that set cement in the pulp cup is cleared conveniently.