Three polysaccharides (GLP-H, GLP-V and GLP-F) were obtained from Ganoderma lucidum by hot air drying, vacuum drying and vacuum freeze drying, respectively. Their chemical compositions were determined, and antioxidant activities were investigated on the basis of superoxide radical, hydroxyl radical, reducing power, DPPH free radical and Ferric-reducing antioxidant power (FRAP) assay. The results showed that three polysaccharides exhibited antioxidant activities in a concentration-dependent manner. Among three polysaccharides, GLP-F and GLP-V had the higher scavenging effects on hydroxyl radicals, superoxide radicals, DPPH free radical, and stronger reducing power than GLP-H. GLP-F showed the stronger antioxidant capacity than GLP-V and GLP-H in FRAP system. GLP-H and GLP-V showed an almost identical pattern in FRAP system (p > 0.05). However, GLP-V showed the stronger radical scavenging activities than GLP-H. Available data obtained in in vitro models suggested that vacuum freeze drying was an appropriate and effective treatment for obtaining the polysaccharide from G. lucidum.