Carrier-free88Y radioisotope, which has the longest half life /T=106.6 d/ of yttrium radioisotopes and is a -ray emitter, was obtained by proton irradiation of strontium, followed by cooling for one month. Then,88Y was purified by precipitating strontium as strontium nitrate and extracting yttrium with tri-n-butyl phosphate /TBP/. The decontamination factor of strontium to yttrium was more than 4×103 and chemically pure yttrium radioisotope was obtained.