Bismuth-based semiconductors are an important family of photocatalysts, in which bismuth oxyiodide is one of those with narrow band gap and excellent visible light response. However, the photocatalytic activity of bulk bismuth oxyiodide is usually not satisfactory, and need to be improved by various strategies. The layered structure of bismuth oxyiodide is very typical in Bi-based photocatalysts, and almost all strategies for enhancing the photocatalytic performance of Bi-based photocatalysts are adaptable for bismuth oxyiodide. Hence the modification of bismuth oxyiodide is of significant referential importance for Bi-based photocatalysts, and has attracted numerous attentions. Herein, we overview the recent advances on the modification of bismuth oxyiodide in this paper, by using the strategies such as structure and morphology control, composite construction and surface modification. The relevant mechanism on promoting the light absorption, charge carrier migration and separation, and tuning the band structure were also summarized. It is believed that this review will provide a guidance for the development of highly efficient visible-light-driven photocatalysts.