In order to ensure that the photovoltaic cells always operate in its MPPT state throughout the entire process of photovoltaic energy storage circuit, A BOOST-BUCK cascaded photovoltaic energy storage circuit is proposed. In the BOOST-BUCK cascaded photovoltaic energy storage circuit, by configuring a small capacity cache capacitor, the BOOST conversion circuit as the front-end circuit achieves the full range MPPT output of photovoltaic cells, and the following BUCK conversion circuit with large capacity energy storage container is utilized to achieve large capacity energy storage. The BOOST-BUCK cascaded photovoltaic energy storage circuit and its MPPT control algorithm are presented, and theoretical analysis and simulation experimental verification are conducted. Theoretical analysis and simulation experiment results indicate that the BOOST-BUCK cascaded photovoltaic energy storage circuit has much better performance than the pure BOOST photovoltaic energy storage circuit, and can achieve maximum power output of photovoltaic cells throughout the entire process under MPPT control.