Abstract: In order to solve the disadvantage of the output power drop of distributed photovoltaics under partial shadow,an improved efficiency optimization strategy for low-voltage DC grid-connected distributed photovoltaic system with modular cascaded structure is proposed. This paper focuses on analyzing the output characteristics of submodules based on distributed maximum power point tracking series output,which shows that the system can output the maximum power in a certain voltage range,and then compares the transmission power loss of the voltage fluctuates with specified range and voltage is balanced through theoretical analysis. Finally,a system-level simulation model is built in Matlab/Simulink environment. The results show that the proposed efficiency optimization control strategy can effectively reduce the transmission power loss and increase the power generation efficiency without increasing the hardware cost of the system.