Water-soluble chitosan with a 50% deacetylation degree was prepared according to the literature. The mixtures of water-soluble chitosan and poly(acrylic acid) (PAA) in water was studied by various experimental techniques, such as viscometry, potentiometry, and transmittance measurements. The results showed that water-soluble chitosan may complex with PAA through electrostatic attraction. This polyelectrolyte complex exists steadily at about an equimolar unit composition.