With the expansion of energy demand and the development of environmental protection.The use of new energy has received more and more attention especially the solar energy which plays an very important part in energy system.Three-level DC/DC converter has important significance for improving solar power generation efficiency.Compared to the traditional two-level DC/DC structure, the Three-Level DC/DC has the advantages of small power loss of switching devices and high efficiency of the entire power generation system,but it has unbalanced power problems in the bipolar DC bus which we called neutral point voltage fluctuation.While the voltage of both DC side is unbalanced,it will increase the harmonics of the system output voltage,and it will also damage the switches. Whether neutral point voltage fluctuation can be handled well is the top priority in research. In order to solve this issue,corresponding modulation strategies and control methods are proposed in this paper.Taking the Three-Level DC/DC converter as research subject,this paper mentions some points as follows.Three-Level DC/DC Converter topology is described and converter operating `principle is introduced in detailed way to make a good foundation for the analysis of the following modulation strategy.After Specif Modulation analysis has been illustrated a Multi-carrier Pulse Width Modulation method is used to keep the bipolar DC bus voltage in balance.Then Select a double closed-loop voltage control strategy to achieve the stability of the whole There-Level DC/DC system.At last we set up models that consists of a voltage input module,a control module and a DC/DC conversion module for simulation.Simulation results are presented to verify the effectiveness of the proposed theory.