Vanadium redox flow battery (VRFB) have emerged as a highly regarded energy storage technology due to their excellent safety and long cycle life. As the core component, the power stack, due to its unique structure featuring series-connected circuits and parallel-connected fluid paths, has shunt currents that do not flow through the load, which in turn affects the system efficiency. To address this issue, this paper analyzes the mechanism of shunt current generation and establishes a quantitative calculation model for shunt currents based on equivalent circuits. Then examines the distribution of shunt currents in the stack during charging and discharging processes, as well as the impact of key parameters such as the number of single cells, state-of-charge (SOC), manifold resistance, and channel resistance on shunt currents. Moreover, the accuracy of the established model is verified using test data from a 32 kW stack comprising 60 single cells, providing design guidance for tens-of-kilowatt class stacks oriented toward residential energy storage.