Titanium dioxide (TiO2) has been a topic of extensively studied metal oxide materials in the last decades, especially in the arena of energy and environmental applications. However, its wide band gap (~3.2 eV) makes it capture only about 5% of solar energy, which greatly hinders its light harvesting efficiency. Recently, the chemistry of structurally defective TiO2 with Ti3+ self-doping (or oxygen vacancies) has been developed to tackle the above challenges. Well-managed defects (e.g. impurity, structural vacancies etc.) in terms of their location and concentration in materials can result in more desired properties. Based on this, we introduce an oxidation-based (Ti2+→Ti3+) synthesis of anatase/brookite TiO2 nanocrystals with various Ti3+ concentrations via a solvothermal/hydrothermal process in combination with post-annealing at different temperatures. The specific contents are as following: (1) The uniformed self-doped anatase TiO2 nanocrystals with high concentration of Ti3+ is synthesized by a oxidation-based solvothermal method, and we studied the H2O2 amount, acidic/weak alkali/strong alkali system dependence of precursor states and products formation. We also explored a HCl washing process to remove impurities, like unreacted NaBH4 and NaBO2 byproduct. (2) By simply controlling the annealing temperature, both concentration and location of the Ti3+ defects can be well managed to reside predominately in the subsurface/bulk regions of the post-annealed anatase TiO2 nanocrystals, a highly desired feature for stable visible light-driver photocatalysis. The location and quantity of the Ti3+ in anatase nanocrystals pinpointed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) suggest that this temperature-mediated management of the location and concentration of Ti3+ defects is achieved through a Ti3+ reversible-diffusion mechanism. As an applicable verification, the sample attained by post-annealing treatment at 500°C, which has the highest Ti3+ concentration predominately in the bulk region, exhibits a 30-fold enhancement in visible-light decomposition of methylene blue and 4 times improvement in the maximal transient photocurrent density compared with P25. The present work underlines the importance of proper distribution of subsurface/bulk Ti3+ defects and give impetus to the development of the “defect engineering” of TiO2 nanocrystals towards high visible light-driven photoactivity. (3) Based on the hydrothermal synthesis method, we developed an effective strategy to prepare uniformed Ti3+ self-doped brookite TiO2 microcrystals. Through a post-annealing treatment, the location of the Ti3+ defects can be effectively controlled predominately in the subsurface/bulk regions of the brookite microcrystals, leading to the remarkably enhanced phocatalytic activity and stability. The type of free radicals produced in the visible-light decomposition of methylene blue process was explored using DMPO as a scavenger，providing insights on the visible ligth driver photocatalysis at Ti3+ self-doped brookite TiO2.