Most of the radioactive waste generated during the decommissioning of nuclear power plants are relatively low in radioactivity, except for the reactor pressure vessel, reactor internals and primary shielding walls, which have high levels of radioactivity. However, the treatment and disposal costs of decommissioning waste account for a high proportion of the total decommissioning cost. In order to minimize the decommissioning waste and to plan the decommissioning costs, it is necessary to study and estimate the total quantity of decommissioning radioactive waste in the design phase. This paper presents the statistical method for estimation of decommissioning radioactive waste quantity, gives the complete steps for estimating decommissioning radioactive waste quantity, and determines the waste quantity estimation principle for each type of decommissioning radioactive waste. Finally, the estimation task based on a Chinese typical million kilowatt nuclear power station single unit is reasonably completed. It is estimated that the quantity of decommissioning radioactive waste generated by this nuclear power station single unit is about 12000m3, which is similar to that of the same type-unit in the world. This proves the rationality of the method for estimating decommissioning radioactive waste quantity proposed in this paper.