In this work, a calculation method of chemical kinetics was established for labeling reaction of ^99mTc-N-ethyl-N₂S₂-memantine, a potential NMDA receptor imaging agent prepared in our laboratory. Four groups of vials (3 vials per group) were added with 0.02 mL (1 mg/mL) N-ethyl-N₂S₂- Memantine, 0.08 mL (40 mg/mL) GH, 0.05 mL (10 mg/mL) EDTA-2Na, 0.035 mL (2 mg/mL) SnF₂, 0.8 mL phosphate buffer(1 mol/L, pH 6.5) and 37 MBq Na^99mTcO₄. The vials were incubated at 70°C, 80°C, 90°C or 100°C. Samples were taken with capillary from the vials at 2, 5, 10, 20, 30, 40 and 60 min. Labeling yields were determined by TLC. Order of reaction n, rate constant k, activation energy E_a and half life t_1/2 of labeling reaction were calculated with the kinetics software we compiled. Mean labeling yields of ^99m Tc-N-ethyl-N₂S₂-memantine at 2, 5, 10, 20, 30, 40 and 60 min were (1) 13.5, 15.7, 34.0, 64.8, 81.9, 91.4 and 95.4 at 70°C; (2) 13.2, 20.5, 40.1, 70.0, 88.2, 94.5 and 95.6 at 80°C; (3) 15.6, 22.9, 43.7, 74.3, 87.2, 93.4 and 96.1 at 90°C; and (4) 20.5, 25.8, 45.3, 81.1, 92.2, 95.6 and 96.0 at 100°C. The other parameters were; n =1; k=0.053, 0.061, 0.063 and 0.076 L/min at 70°C, 80°C, 90°C and 100°C, respectively; E_a=12.38 kJ/L^; t_1/2=13.11, 11.45, 11.05 and 9.07 min at 70°C, 80°C, 90°C and 100°C, respectively. The mean labeling yield increased with temperature and time, optimized at 100°C and 40–60 min. The concentration of ^99mTc-N-ethyl-N₂S₂-Memantine was larger than that of Na^99mTcO₄, so n=1. The k increased with reaction, hence the accelerated reaction rate at higher temperatures. The labeling reaction was not so difficult because of the low E_a. The t_1/2 decreased with increasing reaction temperature, hence the acceleration of labeling reaction.