The aim of this study was to determine the yield, chemical composition, specific rotation (SR), infrared (IR) spectroscopy and the effect on bacterial growth of a crude sulfated polysaccharide (SP) from the red marine alga G. ornata (Go). Go-1 (25°C), Go-2 (80°C), and Go-3 (80°C) were sequentially extracted and yielded 9.2%. The contents of sulfate (5.88-10.3%) and proteins (0.1-3.7%) were small. The values of SR were [µ]D20°f -19.0, -51.0, and -56.5, respectively. IR spectrums showed the presence of galactose-4 sulfate and absence of 3,6-anydrogalactose-2 sulfate, galactose-6 sulfate and galactose-2 sulfate. SR and IR techniques confirmed SPs. Go-3 was tested on the growth of bacteria (Bacillus subtilis, Staphylococcus aureus, Enterobacter aerogens, Escherichia coli, Pseudomonas aeruginosa, Salmonela choleraesuis and Salmonela typhi), but only E. coli was inhibited.