The aim of this work was to provide a preliminary characterization of alkalic-extractable polysaccharides (ALPS) from Coprinus comatus, to explore its in vivo antioxidant activities and protective effects on alcohol-induced liver injury. ALPS showed strong antioxidant and anti-inflammatory abilities and markedly low serum enzyme activities, hepatic and serum lipid levels, as well as low hepatic lipid peroxidation levels; moreover, ALPS improved the alcohol metabolism system. These results were also confirmed by an analysis of histopathological section observations. ALPS, in both α- and β-configurations, as analysed by fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR), was mainly composed of rhamnose (Rha), fucose (Fuc), ribose (Rib), xylose (Xyl), mannose (Man), galactose (Gal) and glucose (Glu) with mass percentages of 0.52%, 1.02%, 0.80%, 0.92%, 3.05%, 2.96% and 90.73%, respectively. These results may offer support for the use of ALPS as a functional food or natural drug source that can prevent and treat alcohol-induced liver injury.