The invention discloses a combined high-efficiency quicklime slaking device comprising a front stand and a rear stand. The front stand is provided with a primary coarse granule slaking area, an primary granule feeding hole of the primary coarse granule slaking area is provided with a quicklime storage bin and a variable-frequency vortex arrester, the primary coarse granule slaking area is internally provided with a first longitudinal stirring component, the rear stand is provided with a secondary slaking area and a complete slaking area, a secondary feeding hole at the front part of the secondary slaking area is connected with a primary discharging hole of the primary coarse granule slaking area, a secondary discharging hole at the rear part of the secondary slaking area is connected with a final feeding hole of the complete slaking area, the back of the complete slaking area is provided with a final discharging hole which is connected with a desulphurization reactor, the secondary slaking area and the complete slaking area are respectively and internally provided with a second transversal stirring component and a third transversal stirring component, a first spraying device is arranged above the primary coarse granule slaking area, and a second spraying device is arranged above the secondary slaking area. The invention can avoid the scaling and the blocking in the device, slake quicklime with poor activity, improve the slaking efficiency, randomly control the addition of materials, reduce the system floor occupation, improve the system stability, decrease the system investment and the system operation cost and omit a primary quicklime screw conveyer and a bag-type dust collector for discharging steam exhaust.