Our continuing search for marine bioactive secondary metabolites led to the screening of crude extracts of sea cucumbers by the model of Pyricularia oryzae. A new sulfated triterpene glycoside, coloquadranoside A (1), together with four known triterpene glycosides, philinopside A, B, E and pentactaside B (2-5) were isolated from the sea cucumber Colochirus quadrangularis, and their structures were elucidated using extensive spectroscope analysis (ESI-MS, 1D and 2D NMR) and chemical methods. Coloquadranoside A possesses a 16-acetyloxy group in the holostane-type triterpene aglycone with a 7(8)-double bond, a double bond (25,26) at its side chain, and two β-d-xylose in the carbohydrate chain. Coloquadranoside A exhibits in vitro some antifungus, considerable cytotoxicity (IC<sub>50</sub> of 0.46-2.03 μM) against eight human tumor cell lines, in vivo antitumor, and immunomodulatory activity.