Background <p>The vaginal microecological barrier in postpartum women is particularly vulnerable, and its stability plays a crucial role in maintaining reproductive tract health. Emerging evidence indicates that <i>Sophora flavescens</i> films (SFF) may have therapeutic potential in managing postpartum vaginal dysbiosis (PVD). This study is therefore designed to evaluate the safety, efficacy, and cost-effectiveness of SFF in the treatment of PVD.</p> Methods and analysis <p>This study is a multicenter, randomized, double-blind, placebo-controlled clinical trial. A total of 292 participants diagnosed with PVD will be enrolled from four tertiary hospitals across China. Eligible participants will be randomly assigned to receive either SFF or a placebo, administered intravaginally once daily for seven consecutive days (each film contains 100 mg of oxymatrine). The primary outcome is the therapeutic efficacy of SFF in improving PVD. Secondary outcomes include changes in vaginal health scores, vaginal inflammation scores, quality of life, levels of vaginal inflammatory biomarkers, incidence of adverse events, and treatment-related costs. Multivariable logistic regression models and analysis of covariance (ANCOVA) will be employed for analysis. Furthermore, a cost-effectiveness analysis (CEA) from the patient’s perspective will be performed using a decision tree model to evaluate the pharmacoeconomic profile of SFF.</p> Discussion <p>This study provides evidence-based insights into clinical interventions for PVD. It uses standardized assessment criteria and a double-blind design. However, the findings may be influenced by subjective judgment and regional limitations. Future multicenter studies are needed. They will validate therapeutic efficacy. This will help optimize clinical decision-making and economic evaluations.</p> Trial registration <p>The study is registered at <a href="http://www.chictr.org.cn">http://www.chictr.org.cn</a> (ChiCTR2500102388, 14 May 2025).</p>