The present invention relates to a homogeneous polysaccharide with an immunoregulatory activity and a preparation method therefor. The homogeneous polysaccharide with an immunoregulatory activity has a single chromatographic peak, the molecular weight of which is 6880 ± 50 Da and the optical value of which is 158.4 ± 0.5°. Infrared spectrometry has an α-configuration saccharide characteristic absorption peak at 847.6 cm-1, the characteristic chemical shift of hydrogen protons in the hydrogen spectrum thereof is δ5.40, δ3.95, δ3.84 and δ3.61, and the characteristic chemical shift of carbon signals in a carbon spectrum is δ99.6, δ76.6, δ73.3, δ71.5, δ71.1 and δ60.4. The homogeneous polysaccharide has the function of enhancing body immunity, can play a good anti-tumor, anti-virus, anti-infection role, etc. in the regulation of immune-related diseases, and has potential development value in the industry of medicine and healthcare products for treating and preventing diseases.