Abstract: A CLLC bidirectional resonant converter used for wide voltage gain range and wide range of load environment was researched. This paper thoroughly analyzed the gain characteristics and resistive boundary of CLLC resonant converter from the perspective of FHA method. Aiming at the shortcomings of traditional design methods in face of non-resistive active loads, a design method based on parameter optimization and ensuring global soft switching operation was proposed. In conclusion, An experimental prototype with 640～900 V input voltage, 200～400 V output voltage and bidirectional power rating of 5 k W was established, which verify the correctness of the theoretical analysis and the feasibility of the proposed parameter design method.