The polysaccharide constituents were extracted and purified from the flowers of Dendrobium officinale Kimura & Migo.Subsequently,their structural characteristics were analyzed,and their immunomodulatory effects were examined at the cellular level.This study aims to furnish a theoretical foundation and methodological reference for the industrial production and application of polysaccharides derived from the flowers of D. officinale.This paper described the extraction of crude polysaccharide from D. officinale dried flowers using aqueous alcohol precipitation.The polysaccharide was then purified using DEAE-52 cellulose and Sephadex G-100 gel chromatography.Its structural composition was analyzed through high-performance gel permeation chromatography,PMP pre-column derivatization,Fourier infrared spectroscopy,and ultraviolet absorption spectroscopy.Additionally,the immunomodulatory activity of polysaccharide from D. officinale dried flowers was evaluated.The isolated and purified polysaccharide from D. officinale dried flowers,with a yield of 0.578%,primarily consisted of mannose,glucose,and small amounts of galactose,xylose,and arabinose in a ratio of 74.388∶22.676∶2.171∶0.173∶0.592,and had an average molecular weight of 2 216 Da.At concentrations of 50-200 μg/mL,polysaccharide from D. officinale dried flowers significantly boosted macrophage proliferation,NO release,and ROS production.Research showed that D. officinale flowers were rich in polysaccharides and had strong immunomodulatory activity,the function was potentially exerted through the TLR4/NF-κB pathway.