BACKGROUND: Selenium nanoparticles (SeNPs), comprising a novel selenium element with higher bioactivity, easily aggregate into large black monomeric selenium particles. In the present study, polysaccharides from the seeds of Plantago asiatica L. (PLP) was used as a template and morphology/particle size modifier to synthesize selenium nanoparticles. The preparation process of SeNPs stabilized by PLP was optimized, and its antioxidant and immunological activities were investigated. RESULTS: The optimal preparation conditions of PLP-SeNPs were a reaction temperature of 60°C, a reaction time of 1.5 h, a PLP concentration of 0.04 mg · mL CONCLUSION: The present study lays a theoretical foundation for the development of food-borne SeNPs and the exploration of their application in functional foods, which will help to promote the high-value utilization of P. asiatica L., and also has an important guiding significance for the healthy development of selenium-enriched functional food industry. © 2025 Society of Chemical Industry.