Abstract: The input parallel output series cascaded DC/DC converter can reduce the current/voltage stress on the switching device,and is suitable for the photovoltaic DC boost system with low voltage input and high voltage output. In order to ensure the stable operation of the cascaded converters,it is necessary to ensure that the output voltages of each module are balanced. The shortcomings of the unified duty cycle control strategy are analyzed,and a current-sharing MPPT control strategy is proposed to achieve output voltage equalization and the maximum power tracking of photovoltaic modules. In view of the shortcoming of the transient characteristics of the current-sharing MPPT control strategy when the light intensity changes. A current sharing and voltage sharing MPPT control strategy is proposed,which superimposes the output voltage loop on the basis of the current sharing loop,so as to improve the dynamic voltage sharing capability of the system. And a modular design structure of the input-parallel output-series cascaded DC/DC converter in the photovoltaic DC boost system is proposed. The simulation results verify the effectiveness of the method.