As the reliability analysis for modular multilevel converter（MMC） usually ignores the correlation between control module and submodules. Firstly， the reliability model of single submodule（SM） and control module is established based on submodule topology analysis. Secondly， considering the interaction of the service life between the SMs and control module， this paper selects the Copula function in accordance with the special application scenario according to the construction method of Copula theory multi-variable joint probability distribution function. Thirdly，taking into account the premise of the correlation of all modules， the MMC reliability analysis model is established with redundant configuration based on k/n（G） model. Finally，taking the flexible DC transmission project in Nanhui Shanghai as an example，the variation law of MMC reliability under different conditions of operation years， correlation degree，requisite SM count and redundant SM count are analyzed. The results show that the model can meet the MMC reliability assessment requirements better and provide the necessary information for MMC topology design and redundancy configuration.