The invention relates to the technical field of optical fiber energy supply, in particular to an optical fiber energy supply system based on a multi-junction concentrating photovoltaic battery and an energy supply method. The optical fiber energy supply system based on the multi-junction concentrating photovoltaic battery is characterized by comprising four parts such as a laser module, an optical fiber coupling module, a light splitting module, photovoltaic conversion modules; the laser module uses a multiband laser module, laser beams output by the multiband laser module are incident to an energy transmission optical fiber after being merged through the optical fiber coupling module and then are incident to the light splitting module after a certain distance of transmission, the light splitting module is used for splitting a laser beam into multiple laser beams, and the split laser beams supply power for load circuits and sensing equipment through the corresponding photovoltaic conversion modules.