The traditional submodule capacitor voltage measuring method requires the same number of submodule voltage sensor, which increases the system costs and burden of data acquisition system. In this paper, a new method based on the nearest level approach to detect the voltage of the MMC submodule is proposed. The method divides the submodule into groups, each group has only a voltage sensor to correct the observer voltage, and the method for improving the number of correction is proposed. Then a compensation method is proposed to solve the delay of voltage sampling circuit affecting the output voltage measurement accuracy. The simulation and experimental results show that the proposed method is correct and effective.