With the development of electric vehicles, L-LLC resonant converters for power transmission have received more and more attention. L-LLC resonant converter has excellent performance, but the additional inductance will increase the reactive power of the converter and reduce efficiency. In this paper, a parameter design method for L-LLC resonant converter is proposed. This method takes the minimum reactive power as objective to select the additional inductance, which can reduce the conduction loss of the converter and improve efficiency. Finally, a 3 kW L-LLC resonant converter prototype using proposed method is built, and the efficiency is compared with the traditional L-LLC resonant converter. The experimental results show that the converter using proposed method has higher efficiency under same operating conditions.