In order to investigate the heterotrophic nitrification and aerobic denitrification ability of Acinetobacter harbinensis HITLi7(T) at 2 degrees C, both the growth parameters and substrates utilization characteristics were tested and appropriated kinetic models were obtained in this study. Under the initial concentration of 5 mg/L, the maximum NH4+-N and NO3--N degradation rates were 0.076 mg NH4+-N/L/h and 0.029 mg NO3--N/L/h, respectively. At the simultaneous presence of 2.5 mg/L NH4+-N and NO3--N, the maximum nitrate removal rate increased to 0.054 mg NO3--N/L/h (1.86 folds), while a slight decrease was observed in NH4+-N removal. Two double-substrate models, Contois-Contois (1) for NH4+-N and TOC, Monod-Contois (2) for NO3--N and TOC matched well with the experimental data. The kinetic parameters were determined as mu(max1) = 0.095 h(-1), B-A1=0.012 mg/L, B-T1=0.784 g TOC/g biomass (R-1(2) = 0.9997), and mu(max2) = 0.032 h(-1), K-N2 = 0.375 mg/L, B-T2 = 1.108 g TOC/g biomass (R-2(2) = 0.9731) by multiple regression equation.