The structure of Carboxymethylpachymaran was characterized using Fourier transform infrared spectroscopy.Morphological changes of carboxymethylpachymaran (CMP) were observed under different solution conditions by atomic force microscopy(AFM).After the carboxymethylation,the solubility of pachyman in the water was significantly increased,its β-D-glucan characteristic absorption peak at 890 cm^-1 became weak obviously,and its methylene vibration absorption peak and CO antisymmetrical stretch vibration absorption peak appeared at 1 333 and 1 606 cm^-1 respectively,which indicated that the carboxymethylation succeeded.The analysis of AFM results showed that CMP molecules existed in different morphology under different solution conditions,and that the concentration,ionic strength and solvent physical chemistry characteristics of polysaccharide solution had effects on the CMP chains conformation and the action mode between different molecular chains.The phenomena were considered to be related to hydrogen bond association and intramolecular and intermolecular electrostatic interactions of CMP.Meanwhile,the affinity and electrostatic interaction between CMP molecules and the mica substrate also had an influence on the CMP chains conformation and the image quality.