The invention relates to a three-port DC-DC converter applied to the efficient energy transmission of a photovoltaic power generation system and a control method of the three-port DC-DC converter andbelongs to the technical field of photovoltaic power generation. The photovoltaic power generation system comprises a photovoltaic solar cell, an energy storage battery, a phase-shifted full-bridge converter and a direct-current bus-bar; and a circuit topological structure is the phase-shifted full-bridge converter multiplexing primary side bridge arm switching tubes; the input of the phase-shifted full-bridge converter is connected with the direct-current bus-bar; the output of the phase-shifted full-bridge converter is connected in series with the photovoltaic cell and then is connected intothe direct-current bus-bar; and the output voltage of the phase-shifted full-bridge converter offsets difference between the voltage of the direct-current bus-bar and the voltage of the photovoltaiccell, so that the photovoltaic cell can be in a maximum power acquisition state. The duty ratio of the primary side bridge arm switch tubes of the phase-shifted full-bridge converter is adjusted, so that the charging and discharging current of the storage battery can be adjusted, and the stability of the voltage of the direct-current bus-bar is maintained. With the topological structure provided by the invention adopted, the efficiency of the whole photovoltaic power generation system can be remarkably improved on the basis of maintaining the voltage stability of the direct-current bus-bar andacquiring maximum photovoltaic power. The three-port DC-DC converter has a bright application prospect.