Abstract: An isonitrile ligand 2,3-dimethyl cyclohexylisonitrile (DMCHI) and its copper salt (Cu(Ⅰ)(DMCHI)_4BF_4) are synthesized and characterized by IR,~1H NMR and elemental analysis.The complexes ~(99)Tc~mN-DMCHI and ~(99)Tc~m-DMCHI are prepared by ligand exchange reaction and directly labeling method,respectively.The results of partition coefficient and stability studies indicate that the complexes are lipophilic and stable over a period of 6 h at room temperature.Biodistribution of the new complexes in mice showe that these two complexes all have high blood uptake and retention in blood very well.The artios of blood-to-heart,blood-to-liver and blood-to -lugn at 5 min post-injection are 6.53,2.11 and 1.27 for ~(99)Tc~m-DMCHI and 5.29,1.79 and 1.18 for ~(99)Tc~mN-DMCHI,respectively.Based on these promising properties it is worthy to develop these ~(99)Tc~m labeled complexes as potential blood pool agents.