Background: Oral mucositis (OM) poses a significant challenge in children undergoing hematopoietic stem cell transplantation (HSCT). There is a gap between clinical practice and the evidence, and nursing practices is not standardized. Objective: This study aims to evaluate the effectiveness of applying the evidence for preventing HSCT chemotherapy-induced OM in children and to elevate the nurses' compliance to the evidence.<br /> Methods: Following the clinical evidence practice application model of the Joanna Briggs Institute (JBI) evidence-Based Care Center. The process included reviewing literature, extracting evidence, identifying gaps, developing audit criteria, conducting a baseline audit, creating an action plan, implementing evidence-based interventions, and assessing outcomes.<br /> Results: After the evidence implementation, 6 out of 12 audit criteria with poor compliance are significantly improved, with statistically significant differences (P<0.05). The incidence of OM decreases, with a statistically significant difference (66.6% vs 36.7%, P=0.02). The incidence of grade I, II, III, and IV OM also decreases (30% vs 23.3%, 23.3% vs 13.4%, 10% vs 0%, and 3.3% vs 0%). Ultimately, the standardized oral care practice routine and workflows to prevent OM were established.<br /> Conclusion: Bridging the gap between evidence and clinical practice can standardize nurse behavior, decrease the incidence of OM, and lower the OM severity in children undergoing HSCT.