In this work, we have applied microstructure management and doping techniques to conventional wide band gap semiconductor CaTiO3 with the aim to improve its light absorption and photocatalytic activity. A series of La/Cr co-doping hollow CaTiO3 cubes have been successfully prepared by a template-free hydrothermal method. Their crystal structures, microstructures, optical absorption and photocatalytic hydrogen production have been systematically investigated. Our results suggest that hollow CaTiO3 owns a higher light absorption than solid one and demonstrates a much better photocatalytic activity both under full range (lambda >= 250 nm) and visible light illumination (lambda >= 400 nm). These improvements probably originate from the peculiar hollow microstructures that increase photon-matter interactions and shorten the charge migration pathways. The photocatalytic activity for hydrogen production has been further studied by varying the La/Cr content in CaTiO3. An optimal doping point at 5% La/Cr doping level has been reached for full range illumination with apparent quantum efficiency approaching similar to 2.41%. Nevertheless, the activity under visible light illumination shows a clear dependence on doping level with highest apparent quantum efficiency similar to 0.40% at 20% La/Cr doping level. DFT calculations reveal the critical role of Cr in forming a new spin-polarized valence band inside the original band gap of CaTiO3 therefore is responsible for band gap reduction and visible light photocatalysis. This work here highlights the importance of microstructure control to the photocatalytic performance and shall shed a light on the design and development of efficient photocatalytic materials/systems.