Pleurotus ferulae is an edible mushroom and has been used in Uygur medicine for a long time. In this study, we purified polysaccharides from P. ferulae (PFPS) and investigated its structural characteristics. We obtained a homogeneous PFPS with a molecular weight of around 1600 kDa and prominent characteristic polysaccharide groups, which mainly contained glucose (97%), followed by mannose and galactose (3%). Both 1H and 13C NMR spectra indicated that PFPS contained both α- and β-anomeric configurations. Atomic force microscopy and Congo red-staining data further suggested that PFPS belonged to a linear branched structure that existed in flexible single chains at low concentrations and could form aggregates such as a triple-helical structure at high concentrations. Moreover, PFPS promoted the maturation of dendritic cells through a TLR4 mediated signaling pathway, which is characterized by the increased expressions of CD40, CD86, IL-12 and TNF-α and the decreased endocytosis. The results suggest that PFPS has immunoregulatory activities.