Abstract: One of the most important reasons that cause tumor is decrease or complete absence of apoptosis of tumor cells.Conversely successful anti-tumor therapy is correlated with the introduction of apoptosis into tumor cells.Radiola-beled annexin V is used to image in vivo the phosphatidylserine (PS)that explode on the outer surface of cell membrane after apoptosis so that apoptosis can be detected on the early stage.This imaging method can be introduced into the re-search of tumor in order to help direct the choose of tumor therapy,inspect the effect and evaluate the prognosis.