Acute renal injury (AKI) is a serious disorder of renal failure or renal damage that occurs within hours or days. At present, there is no approved pharmaceutical treatment for AKI. Zebrafish is an excellent model for studying the repair of AKI because of its remarkable ability to repair kidney injury. Using zebrafish AKI model inducing by gentamicin, we found that hydrogen peroxide (H2O2) plays dual roles during the period of AKI recovery including renal repair and kidney regeneration. In the repair stage of AKI, H2O2 was produced in proximal and distal segments of renal tubules. By inhibiting H2O2 generation using Duox Vivo-Morpholino or chemical inhibitor, it was observed of severe damage of renal tubules, and extensive cell apoptosis. In the stage of regeneration, we found that H2O2 was highly generated in renal interstitium. Inhibiting production of H2O2 could significantly down-regulate the ability of kidney regeneration, which was associated with the failure of proliferation of renal progenitor cells. Therefore, H2O2 acts as a protective factor in renal repair and an initial signal of kidney regeneration, indicating the key roles of H2O2 in promoting recovery of AKI in zebrafish. (C) 2019 Elsevier Inc. All rights reserved.