This study aimed to evaluate the polysaccharide contents and antioxidant activities of 14 important wild mushroom species in the Lesser Khingan Range Forest of northeastern China. The fungal species were identified by morphology and DNA matching, belonging to six families: Polyporaceae (four species), Tricholomataceae (three), Russulaceae (three), Lepiotaceae (two), Lycoperdaceae (one), and Paxillaceae (one). Polysaccharides were isolated and partially purified from the water extract of each m ushroom by ethanol precipitation, deproteinization, and dialysis. Antioxidant activities of the mushroom polysaccharides were found to vary with both the species and the assay methods, and the highest three were from Handkea utriformis (535.8 μmol trolox/g), Macrolepiota mastoidea (378.6), and Armillaria ostoyae (329.1) in radical scavenging; H. utriformis (5.94 mmol Fe/g), Lepista nuda (4.65), and A. ostoyae (4.42) in reducing power; and Armillariela cepistipes (484.6 μmol Fe2+/g), H. utriformis (274.8), and M. mastoidea (202.5) in Fe2+ chelating. Several of the polysaccharides showed notable anti-tyrosinase activities, and that of Chroogomphus rutilus was the most potent with an IC50 of 0.46 mg/ml. These wild mushrooms can be useful sources of polysaccharides as potential antioxidants and tyrosinase inhibitors. This is the first systematic study on the wild mushroom species, as well as their polysaccharide contents and biological activities, from this forest.