In this paper, a high gain modular multilevel dc-dc converter topology is proposed. As compared with the conventional modular multilevel step-up converters, the proposed converter offers an additional degree of control-freedom and higher steady-state voltage gain. The proposed converter operates in continuous conduction mode. A detailed small-signal modeling for the proposed converter based on state-space average modeling is presented. In addition, this study covers both the small-signal and steady-state analysis for the high gain modular multilevel dc-dc converter operating in continuous conduction mode. The performance of the proposed converter is compared with conventional modular multilevel dc-dc converter. To confirm this design, simulations have been carried out on a 1 kW, 48 V to 288 V converter system. Finally, the validity of the converter is verified by simulation results.