The invention provides a hydraulic puller, and relates to a hydraulic tool which can be operated in narrow space and used for disassembling a coupling which is a transmission component between a motor and a pump. The hydraulic puller mainly solves the problems that an existing method for disassembling the transmission component, namely the coupling, between the motor and the pump comprises the steps of heating the coupling through flames and making the coupling retreat through knocking of a copper rod, the coupling and a bearing expand with heat at the same time and fail to retreat smoothly, the coupling and the bearing are prone to damage in the knocking process, much labor and time are consumed, and potential safety hazards are caused to operation of the pump. The hydraulic puller comprises a puller back plate and a hydraulic cylinder connected to the puller back plate. The hydraulic puller is characterized in that an oil injection hole communicated with the hydraulic cylinder is formed in the puller back plate in the radial direction, and U-shaped bolt holes are formed in pull rod beams at the two ends of the puller back plate. According to the hydraulic puller, the oil injection hole of a traditional hydraulic puller is formed in the side face of the back plate instead, so that the installation length of the hydraulic puller is reduced, space is saved, the U-shaped bolt holes are formed in the pull rod beams, and therefore the hydraulic puller can be used for disassembling couplings with different diameters. The hydraulic puller is high in work efficiency and brings convenience to disassembly.