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Nonradiative wireless power transfer is a popular technology that transfers energy over medium range via strongly coupled magnetic resonance. We investigated the effect of transmit diversity on power transfer efficiency under multiple transmitters. We derived closed-form equations for the power transfer efficiency and the optimal load from both coupled mode theory and equivalent circuit model analyses. We also showed that the analytical results obtained from the two types of analysis are basically the same, so they can be expressed as an equivalent equation that consists of a quality factor and coupling coefficient. In addition, we performed simulations using the Ansoft High Frequency Structure Simulator and the Agilent Advanced Design System to demonstrate the accuracy of our analysis. The results show that a multiple-transmitter wireless power-transfer system can improve power transfer efficiency over all regions in both an angular aligned scenario and an angular misaligned scenario, due to the diversity in the transfer of power.