To explore the biological properties of a new neutral myocardial imaging agent 99mTcN(NOEt)_2,preparation and characterization of 99mTeN(NOEt)_2, kinetics of blood-drug clearance in rabbits, biodistribution in rats, test of undue toxicity in mice and myocardial imaging in dogs were performed and volunteer imaging. Radiochemical purity of 99mTeN(NOEt)_2 was over than 90% and stable for 6 hours at room temperature. Blood disappearance was analyzed with biexponential model, T1/2(α)=2.53 min, T1/2 (β)=330 min and Cl=378 mL/h were obtained. Biodistribution studies demonstrated that 99mTcN(NOEt)_2 localized selectively in myocardium of rats. Cardiac uptake were 2.79, 2.25, 2.00 and 1.88%ID/organ at 5, 30, 60 and 90min of postinjection, respectively. The heart-to-lung activity ratio was 1.16 at 60 min. Images showed that pulmonary uptake decreased faster than cardiac uptake in a dog. The mean heart-to-lung activity ratios in a dog were 1.69, 2.40 and 2.55 at 10, 30 and 60min of postinjection, respectively. The heart was distinguishable on scans at 30min. Whole body imaging showed that cardiac uptake was 2.82%ID at 90min, but hepatic uptake was 30%ID and remained constant. The test of undue toxicity showed that the dose received by mice was 614 times as by human. Volunteer imaging suggests 99mTcN(NOEt)_2 redistribution with time. 99mTcN(NOEt)_2 exhibited favorable stabilities, biological properties and safety. It is worth for further studying in human. To explore the biological properties of a new neutral myocardial imaging agent 99mTcN (NOEt) _2, preparation and characterization of 99mTeN (NOEt) _2, kinetics of blood-drug clearance in rabbits, biodistribution in rats, test of undue toxicity in mice and myocardial imaging Radiochemical purity of 99mTeN (NOEt) _2 was over than 90% and stable for 6 hours at room temperature. Blood disappearance was analyzed with biexponential model, T1 / 2 (α) = 2.53 min, T1 / Biodistribution studies demonstrated that 99mTcN (NOEt) 2 localized selectively in myocardium of rats. Cardiac uptake were 2.79, 2.25, 2.00 and 1.88% ID / organ at 5, The heart-to-lung activity ratio was 1.16 at 60 min. Images showed that pulmonary uptake decreased faster than cardiac uptake in a dog. The mean heart-to-lung activity ratios in a dog were 1.69, 2.40 and 2.55 at 10, 30 and 60min of postinject Whole body imaging showed that cardiac uptake was 2.82% ID at 90min, but hepatic uptake was 30% ID and remained constant. The test of undue toxicity showed that the dose received by mice was 614 times as by human. Volunteer imaging suggests 99mTcN (NOEt) _2 redistribution with time. 99mTcN (NOEt) _2 showing favorable stabilities, biological properties and safety. It is worth for further studying in human.