In order to investigate the influence of capacitance on the mass sensitivity of quartz crystal microbalances in oscillating circuits, an equivalent circuit model impedance analysis method for oscillating circuits is proposed. Firstly, an equivalent circuit model was established, and the relationship between impedance and frequency was analyzed, revealing the correspondence between capacitance and mass sensitivity; Secondly, multiple physical field coupling simulation experiments were conducted to explore the influence of capacitance on the mass sensitivity of quartz crystal microbalances; Finally, an experimental system platform was built and a quartz crystal microbalance mass sensitivity experiment was conducted. The results indicate that parallel capacitors have a relatively small impact on the mass sensitivity of quartz crystal microbalances; When a 1.01pF capacitor is connected in series, the mass sensitivity increases by 8.01×10-2 Hz/ng, and when a 15.84pF capacitor is connected in series, the mass sensitivity increases by 1.49×10-2Hz/ng. This conclusion helps to better understand the influence of capacitance on the mass sensitivity of quartz crystal microbalances, providing strong support for the portable and miniaturized design of the sensor.