Abstract: Effects of characteristics of chitosan and pectin,chitosan / pectin ratio,solution p H and polymer concentration on the turbidity and ζ- potential of solution were investigated and the affecting mechanisms,electrostatic complexation between chitosan and pectin were elaborated by combining the microstructure of complex.The results showed that chitosan with medium molecular weight( 15 × 104) react more easily with pectin to form large complexes,while the deacetylation degree of chitosan had small effect on turbidity of complexation solution.High methoxyl pectin could form compact complexes with chitosan.With the addition level of pectin increasing,the microstructure of complexes changed from loose and sparse to more compacter,and the turbidity of solution showed 4 phases.The ζ- potential of complexation particles became 0 at pectin addition level of with82%( w / w),but the turbidity of solution didn't reach the maximum.When the solution p H was between 3.0 and 4.0,chitosan and pectin were easiest to interact with each other to form complexes with a even,dense structure and the solution had higher turbidity.The complexes formed by chitosan and pectin with various concentrations showed significant different structure because of the effects of polymer concentration on stretch of molecular chain and polyelectrolyte complexation.