Abstract: The labeling of EDTMP(ethylenediamine N,N,N',N' tetrakis (methylenephosphonic acid)) with carrier free 188 Re from the 188 W/ 188 Re generator is investigated in detail. Under the optimal conditions, the labeling yield is more than 98%. The stability of 188 Re EDTMP diluted with 0.9% NaCl is also studied. It is found that the in vitro stability of 188 Re EDTMP is influenced by the addition of carrier. Biodistributions of carrier free and carrier added 188 Re EDTMP in mice is measured respectively. The radioactive absorption of thyroid for carrier added 188 Re EDTMP is obviously less than carrier free one and bone uptake for carrier added 188 Re EDTMP is more than carrier free one. It shows that the addition of carrier could improve the stability in vitro of 188 Re EDTMP obviously and the stability in vivo of 188 Re EDTMP slightly.