The antioxidant activity of purslane juice was compared with that of purslane juice after keeping in cold storage for one year. The juice of Portulaca oleracea and fresh juice of Portulaca oleracea were extracted after one year of cold storage, and the changes of antioxidant activity were evaluated by DPPH radical scavenging method (DPPH) and cerium ion reduction colorimetry (CERAC). Median effective concentration (EC₅₀) was used to compare the antioxidant activity. The EC₅₀ of purslane juice stored at 4℃ for one year to scavenge DPPH free radical was 21.0%; the EC₅₀ of purslane fresh juice scavenging DPPH free radical was 19.7%; the EC₅₀ of purslane juice reduced to Ce (Ⅳ) after storage for one year was 35.0%, and the EC₅₀ of purslane fresh juice reduction to Ce (Ⅳ) was 28.3%. Therefore, cold storage had a certain effect on the antioxidant activity of purslane juice, which could decrease the antioxidant activity of Portulaca oleracea juice.