The Super Kamiokande-Gadolinium (SK-Gd) project is the upgrade of the Super-Kamiokande (SK) detector in order to discover Supernova Relic Neutrinos (SRNs) by loading 0.2% of Gd$_2$(SO$_4$)$_3$ into a 50 kton of the SK water tank. In order to continue solar neutrino measurement with low energy threshold at $\sim$3.5 MeV, radioactive isotopes (RI) should be reduced before loading.
In this talk, the methods to measure RI in Gd$_2$(SO$_4$)$_3$ and the current status of RI background reduction will be presented.