The anti-tumor effect of Glycosaminoglycan from sanguinolaria acutas on Hela cell, CNE-2Z cell and K562 cell in vitro were analyzed by MTT colorimetric method. Results showed that the GAG had anti-tumor activity and the anti-tumor effect of GAG ranged with its concentration. In synergistic inhibition effect of GAG with positive drug (5-Fu) on tumor cells have a simple addition effect or synergistic effect.