Abstract: Effects of NaCl and its concentration on electrostatic self-assembly behavior between chitooligossacharide and pecin were investigated through measurement of turbidity and ζ-potential of chitooligassacharide/pecin complex solution, and analysis of macroscopic and microscopic state of complex solution and turbidity titration procedure with the study on analysis of ATR-FTIR spectrum and ultrastructure of PEC by SEM and TEM. The results showed that NaCl hindered the self-assembly interaction between chitooligossacharide and pectin resulting in decrease of pHc、pHФ and pHprep values. The turbidity of complex solution decreased in phases and the solution became clear with NaCl concentration increasing; meanwhile, the amount of PEC formed decreased and PEC changed to small even nano-particles (NaCl concentration of 30 mM or more) from networks. At NaCl concentration below 10 mM, the intermolecular electrostatic repulsion of pectin decreased and pectin chains became properly flexible and could be rolled and folded to form larger particles with chitooligosaccharide. Further increasing of NaCl concentration, however, led to increase ofζ-potential absolute around the surface of PEC particles and electrostatic repulsion interaction among the particles, which resulted in a better packing of more flexible and coiled pectins with chitooligosaccharide to form more dispersive and less particles. The ATR-FTIR result of PECs implicated that the interaction between chitooligosaccharide and pectin was not changed by addition of NaCl, but intensity of the interaction was. The modes of self-assembly interaction between chitooligosaccharide and pectin at various NaCl concentrations were suggested at the end of this paper.