As a new type of model animal, zebrafish is more and more widely used in the brain-related researches. However, there is a lack of high-resolution imaging technologies for the in vivo characterization of the brain of zebrafish from its infancy (>7 days old) to adulthood. In this study, optical coherence tomography (OCT) is used to give in vivo imaging of zebrafish brains after hatching 21, 45 and 100 d. The results show that the imaging depth and resolution of OCT are both enough to visualize the whole brain of zebrafish from three age groups, and the brain structural features of OCT images match well with the sectional staining results. Both the 2D and 3D OCT results quantitatively show that the zebrafish brain increases significantly in 80 d, however due to tissue atrophy, the sectional staining results can not accurately or quantitatively evaluate the brain''s development. This study shows that OCT can be used as a tool for efficient in vivo imaging and used for the brain''s development research based on zebrafish.