The distribution of physicochemical properties inside the battery, which is difficult to measure using experimental methods, has a significant impact on the performance of the battery. Therefore, based on the numerical simulation method, this paper established a three-dimensional transient model of a zinc-nickel single-flow battery considering the tabs for the first time. The model is based on universal conservation laws (mass, momentum, and charge) coupled with global reaction dynamics. On this basis, the influence of tabs on the physicochemical property distribution in the battery was studied, including the change of ion concentration, current density, overpotential, and local state of charge distribution with time and space. Based on overpotential distribution and ion concentration distribution, the effects of tab size, position, and number on voltage loss and ion concentration distribution were investigated. The results show that the extreme values of various physicochemical properties always appear in the region near the tabs, and the chemical reaction rate in the region near the positive electrode tab decreases significantly in the later period of discharge. The voltage loss of the positive electrode is greater than that of the negative electrode during discharge, especially in the later period of discharge. Also, at the end of discharge, the maximum value of the local charge state of the negative electrode appears in the region near the positive electrode tab. In addition, increasing the length and number of tabs can effectively reduce the voltage loss and improve the uneven distribution of ion concentration; however, when the number of tabs is larger than two sets, this effect is obviously weakened. However, changing the position and width of the tab has little effect on voltage loss and ion concentration distribution.