Radionuclides ^186,188Re, suitable for tumor therapy and with high specific activity, are prepared through irradiating natural metallic rhenium, instead of costly enriched target. Complexation of rhenium with HEDP(1-hydroxy ethylidene diphosphonate) is mainly dependent on pH values and the reductant concentrations in the medium, and the yield is not less than 0.95 in pH 2.0~4.0 and Sn(II) concentration of 0.012~0.018 mol/L. The ^186,188Re-HEDP complex has high stability in vitro and in vivo in the presence of protecting agent, and gives superior biological properties in small animals, similar to those of ¹⁵³Sm-EDTMP including faster blood clearance, lower soft tissue residue and higher skeletal uptake with the peak of 0.2576ID/g at 1h post injection (overseas report 0.0101 ID/g) comparable to that of 153Sm-EDTMP(0.2644ID/g) at 3h post injection.