Chitosan was used in this study to form polyelectrolyte complex (PEC) with water-soluble acidic polysaccharides, including gum arabic and pectin. Porous membranes made of gum arabic or pectin only were quiet fragile. After incorporating with chitosan, the usability of the membranes was greatly improved. The results showed that the gum arabic/chitosan composite membranes had detectable tensile stress and elongation capability. Moreover, the pectin/chitosan composite membranes had significantly improved tensile stress and elongation capability. Both of the two composite membranes had greater water uptake capability than the membranes composed of chitosan only. We have demonstrated that chitosan can function as a material stabilizer to maintain the solid status of the acidic polysaccharides and thus improve the performance of these acidic polysaccharides.