Recently, microRNAs (miRNAs) have been found to mediate the development of diabetic kidney disease (DKD) by regulating podocyte injury. The aim of this study was to investigate the influence of miR-504-3p on high glucose (HG)-treated mouse renal podocytes (MPC5) and its potential regulatory mechanisms. First, a DKD cell model was established. Next, RT-qPCR was performed to measure miR-504-3p and HNF1 Homeobox B (HNF1B) expression levels. Additionally, the proliferation and apoptosis of MPC5 cells were assessed using CCK-8 assay and Flow cytometry, respectively. The protein expression levels of cell fibrotic markers, podocyte injury marker, epithelial-mesenchymal transition (EMT) markers and HNF1B were measured by Western Blotting. ROS, MDA, SOD and GSH kits were used to assess oxidative stress levels. Furthermore, the interplay between miR-504-3p and HNF1B was confirmed by luciferase reporter experiments. The miR-504-3p expression was significantly upregulated in GEO database (GSE161884) and in HG-induced MPC5 cells. The results revealed that HG treatment decreased MPC5 cell proliferation, promoted cell apoptosis and fibrosis, and ultimately led to podocyte injury. However, miR-504-3p knockdown could reverse these phenotypes and reduce podocyte injury. Moreover, online database screening combined with dual luciferase reporter assay confirmed HNF1B as a specific target of miR-504-3p. Finally, overexpression of HNF1B mitigated the proliferation inhibition and apoptosis promotion induced by oxidative stress and inhibited EMT-mediated cell fibrosis, thereby counteracting the effects of miR-504-3p on podocyte injury under HG treatment. In summary, our data indicate that miR-504-3p regulates HG-induced podocyte injury by sponging HNF1B, providing a new direction for the treatment of DKD.