When external disturbances occur, the bus voltage of a MVDC distribution system with PV integration will fluctuate, posing challenges to the stable operation of the power system. In this paper, a PV constant voltage control strategy based on improved linear active disturbance rejection control (LADRC) is proposed to address the insufficient disturbance rejection of traditional PV constant voltage control strategies. For the two-stage integrated DC/DC converter, a linear extended state observer (LESO) based on differential feedback is used to design the improved LADRC structure, and the parameter tuning, disturbance rejection, and stability of the controller are analyzed in detail. The effects of PV constant voltage control using PI control, traditional LADRC, and improved LADRC are compared on a simulation platform. The results show that the PV constant voltage control strategy based on the improved LADRC has excellent anti-interference capability and can restore the DC bus voltage to stability with smaller overshoot and faster response speed.