Considering the reliability of modular multilevel converter (MMC) closely related to key component parameters, a novel parameter estimation method is proposed for insulated gate bipolar transistor (IGBT) of submodule (SM) in MMC. The relationship between the switch status and the voltage of submodule is analyzed and the model of the bridge arm voltage is established. Kalman filtering theory is introduced against the measurement noise of the bridge arm data from sensors. Under the linear minimum variance criterion, the model of the IGBT parameter monitoring information in MMC submodule is established to obtain the IGBT parameters from each submodule in the bridge arm. The substantial reduction in the number of voltage sensors improves the system reliability and decreases its cost and complexity. This method can also effectively eliminate the influence of sensor noise. Finally, the effectiveness of the proposed technique is validated via a PSCAD/EMTDC simulation analysis of a three-phase MMC-HVDC. The method has certain reference value for improving the portability of the monitoring system and reducing the cost and energy consumption.