A series of norcantharidin and bridged perhydroisoindole derivatives were evaluated for their antioxidant and radical scavenging activities. Different in vitro methodologies, such as total reducing power, 1,1-diphenyl-2-picryl-hydrazil (DPPH center dot) free radical scavenging, superoxide anion radical scavenging and metal chelating activities were used. Among the 11 tested compounds, 7 compounds showed potent reducing power activity and 7 compounds showed potent superoxide anion radical scavenging activity. All the tested compounds exhibited potent free radical scavenging ability. The results showed that the synthesized compounds have effective antioxidant power.