A two-dimensional transient model for the study of zinc-nickel single flow battery was developed. The model is based on a comprehensive description of mass, momentum and charge transport and conservation, combining with a global kinetic model for reactions involving ions and proton. The model is validated against the experimental date and is used to study the effects of variations in concentration, flow rate, and applied current density. The model results indicate that increasing the initial concentration of hydroxide ions can increase the discharge voltage of the battery without increasing the ions concentration polarization, and higher zinc ion concentration can slightly decrease the discharge voltage. An increase in flow rate leads to a more rapid generation or consumption of the reactant concentration, a faster mass transfer and a more uniform distribution of the ion concentration. However, the effect of flow rate on the discharge voltage of the battery is small and limited. Bulk reaction rate depends on the applied current density. As the applied current density increases by one or two time, ion concentration polarization in reaction zone and the transfer current density almost double or triple and the over-potential increased a fixed amount each time.