With the development of wireless power transfer technology, MIMO-WPT systems with multiple transmitters and multiple receivers have emerged. MIMO-WPT systems can simultaneously supply power to multiple electrical devices, representing a significant development direction for future wireless charging technology. This paper establishes a system model to analyze the relationship between the voltage and current at the receiving end and the transmitting end. It proposes a parallel output power control method for MIMO-WPT systems based on voltage modulation. By calculating the required input voltage and adjusting the DC/DC circuit in the inverter's front stage, output power control is achieved. Voltage modulation effectively controls the power at each output end, increasing the flexibility of energy transfer and providing methodological reference and theoretical support for the practical application of MIMO-WPT systems.