The invention provides a vacuum drying method for radioactive waste resin. The method comprises the following steps: sending the radioactive waste resin into a dryer in a hydraulic conveying manner; removing most free water in the dryer by utilizing a pneumatic diaphragm pump; heating the dryer by utilizing hot oil, drying the radioactive waste resin under a negative pressure condition and monitoring the resin temperature on the wall and at the center of the dryer; and stopping drying when the material temperature in the dryer reaches a preset value, and then unloading. The vacuum drying method for radioactive waste resin provided by the invention mainly has the advantages of low water evaporation temperature, high evaporation rate, difficulty in decomposing and caking of resin, excellent drying volume reduction effect, and the like under the negative pressure condition, so that the vacuum drying method can be used for replacing a common cement solidification technique in the field of treatment for radioactive waste resin of a nuclear power plant in China.