Total polysaccharide (i.e., GLP-UCE) was effectively isolated from the crude polysaccharide extract powder of Ganoderma lucidum by ultrasonic-circulating extraction, which was separated into three fractions (i.e., GLP-U40, GLP-U60, and GLP-U80) by ethanol fractional precipitation. The detection of antioxidant enzymes (GSH-Px, SOD) and oxidation metabolites (MDA, LF); liver function test of ALT, AST, and LDH; and western blot for antioxidant proteins of GSH-Px and MMP-2 showed that the GLP-UCE displayed a favorable in vivo antioxidant and hepatoprotective activities for reducing the oxidative damage in CCl4-hepatopathy SD rats. The GLP-UCE and its fractions were analyzed and compared by Fourier transform infrared (FT-IR), high-performance liquid chromatography, high-performance gel permeation chromatography, and antioxidant activity in vitro assay. These studies revealed that the fraction GLP-U80 exhibited stronger antioxidant activities in vitro than that of GLP-UCE and other fractions (p<Mw) of 1.05 × 104 g·mol-1 and composed of D-mannose, D-ribose, D-glucose, D-galactose, and L-fucose in a molecular ratio of 1:0.26:8.26:0.64:0.08.