Glyco saminoglycan PG2- 3- 2 from whole viscera of Pinctada martensis was obtained af ter extraction and purification. The fraction showed that its migration rate was relatively near to that of Chondroitin 6- sulphate ( C- 6- S) by acetate film electrophoresis. The infrared spectra ( IR) of it was similar to that of C- 6- S. The result of antitumor test in vivo demonstrated that PG2- 3- 2 could obviously enhance the sensitivity of inhibitive funct ion of clinical antiturmor drugs, the inhibit ion rates of which to Sarcoma 180 and Ehrlich. s Ascipes Carcinoma( EAC ) were 61. 96% and 46. 3% respectively. Moreover, PG2- 3 - 2 had certain function of ant icoagulant by the test in vitro.