Abstract: The current quantification methods of power system frequency strength usually assume that the voltage magnitude at each node is constant. However, during the process of frequency disturbance, the voltage at each node is not constant and may affect the system frequency through various pathways such as influencing loads. Therefore, the assumption of constant voltage may lead to the conclusion with the inaccurate quantification results, or even erroneous conclusions. Therefore, a quantification method of power system frequency strength considering voltage dynamics is proposed. First, a frequency response model for the system that considers voltage dynamics is established, in which the influence of voltage dynamics on the system frequency is characterized by a global coupling term, revealing the interaction paths between voltage and frequency. Based on this, the specific effects of various devices and loads that consider voltage dynamics on the system frequency are analyzed, including the grid-forming converters employing hybrid synchronization control, grid-following converters with additional frequency or voltage outer loops, and constant impedance-constant current-constant power（ZIP） static loads and asynchronous motor loads with distinctive voltage characteristics. Next, by partitioning and decoupling the voltage coupling term and performing unified and simplified modeling, the frequency support capability of each zone in the system as well as the overall frequency strength is quantitatively analyzed. Finally, the effectiveness of the proposed method for quantifying frequency strength is validated through simulations.