A new alkaloid, identified as 1-benzyl-2-nitroso-1,2,3,4-tetrahydroisoquinoline-6,7-diol, named oleraisoquinoline (1), and five organic acids and two esters, identified as 5-(hydroxymethyl)furan-2carboxylic acid (2), 1H-pyrrole-2,5-dicarboxylic acid (3), (7E,10E)-octadeca-7,10-dienoic acid (4), (10E,13E)-octadeca-10,13-dienoic acid (5), (7E,10E)-hexadeca-7,10-dienoic acid (6), methyl tridecanoate (7) and methyl (9E,12E)-octadeca-9,12-dienoate (8), were isolated from Portulaca oleracea L., among which compounds 2 and 4-7 were isolated for the first time. Moreover, the antiinflammatory activities of compounds 1-3 were studied, especially, compound 1 presented good inhibitory effects on the production of inflammatory factors IL-1β and TNF-α.