To optimize the extraction conditions of polysaccharides from Portulaca oleracea L.by ultrasound-assisted enzymolysis method and extraction yield as evaluation index.Methods: Effectiveness of enzymatic hydrolysis and ultrasonic treatment on the structure of Portulaca oleracea L.polysaccharides was evaluated through the near infrared spectral analysis,the non-enzymolysis and without ultrasound-assisted treatment was used as control.The results showed that the optimal extraction conditions of ultrasound-assisted enzymolysis method were as follows: cellulase 2.5%,ultrasonic temperature 60 ℃,ultrasonic power 70W,ultrasonic time 20min.Under these conditions,the yield of crude polysaccharide was up to 18.40%.The result of near infrared spectral analysis showed that enzymatic hydrolysis and ultrasonic assisted extraction technology improved the extraction yield of polysaccharides with no significant effect on the structure of Portulaca oleracea L.polysaccharides.Portulaca oleracea L.polysaccharides had remarkable total antioxidant capacity,and good scavenging activities on DPPH· and ·OH.Furthermore,the scavenging activity had a significant correlation with polysaccharides concentration.