The structural feature of agar polysaccharides from Porphyra haitanensis grown in south China and transplanted to the north was investigated by fractioriation on DEAE - Sephadex A 50, chemical analysis, and infrared and 13C - NMR spectroscopy.The agars composed mainly of Charged molecules were eluted from DEAE - Sephadex A 50 with 1.0 mol/L- NaCl solution from the southern P. haitanensis and with 0.5 mol/L NaCl from the northern one. The 13C-NMR spectra showed that agarobiose [(1 -3)- B D - galactopyranosyl - (1 -4)-3,6-anhydro-a-L-galactopyranose] and the biological precursor of agarobiose [(1-3} B-D-galactopyra nosyl- (1-4)- 6- sulfate-a- L-galactopyranose ] were the major disaccharide repeating units in the charged fractions. The content of the biological precur sor in the agar polysaccharides from southern P. haitanensis was higher than that in the northern one, the content of the biological precursor extracted from cold water was higher than that from hot water, and the content of 6- OMe-D-galactos The structural feature of agar polysaccharides from Porphyra haitanensis grown in south China and transplanted to the north was investigated by fractioriation on DEAE-Sephadex A 50, chemical analysis, and infrared and 13C - NMR spectroscopy. The agars composed mainly of Charged molecules were eluted from The 13C-NMR spectra showed that agarobiose [(1 -3) - BD - galactopyranosyl - DEAE - Sephadex A 50 with 1.0 mol / L NaCl from the southern P. haitanensis with 0.5 mol / L NaCl from the northern one. (1 -4) -3,6-anhydro-aL-galactopyranose] and the biological precursor of agarobiose [(1-3} BD-galactopyra nosyl- (1-4) the major disaccharide repeating units in the charged fractions. The content of the biological precur sor in the agar polysaccharides from southern P. haitanensis was higher than that in the northern one, the content of the biological precursor extracted from cold water was higher than that from hot water, and the content of 6-OMe-D-galactos