Oral lichen planus (OLP) is a common chronic inflammatory disease of the oral mucosa and is considered a precancerous condition. It is characterized by white reticular changes in the oral mucosa, which can progress to erosions and cause pain in severe cases. The pathogenesis of OLP is still unclear, but it is believed to be a T-lymphocyte-mediated autoimmune disease. Currently, only symptomatic treatments are available, and there is no definitive cure. In this project, we plan to use TCM differentiation to categorize OLP patients and conduct a randomized controlled clinical trial to demonstrate the enhanced therapeutic effect of paeoniflorin combined with photodynamic therapy for OLP. The implementation of this project will provide new insights into the clinical management of OLP, improve our understanding of the treatment mechanisms, and have important theoretical and clinical implications.