Polyaspartic acid (PASP) is an environmentally benign agent for the dissolution of calcium salt deposits. In this study, the chelating power of PASP with calcium is investigated by performing the potentiometric titration against PASP solutions. It was found that PASP is fully deprotonated at pH 7. The titration curves are successfully modeled by assuming that four aspartyl residues from an actual PASP molecule consist of a hypothetical molecule (denoted as H4L) that has four distinct acid moieties (four dissociation constants). The resulting dissociation constants and calcium-binding constants for PASP are critical to understanding the dissolution behavior of calcite in PASP solutions. The batch dissolution of calcite powder in PASP solution at four different initial pHs (10, 7, 5, and 3.5) are performed to explore the effect of PASP chelating chemistry on the dissolution behavior of calcite (CaCO3). The results show that PASP replaces interfacial water to react with calcite at high pH (greater than or equal to7) and the dissolution of calcite can be described by a surface adsorption and complexation mechanism. At low pH (less than or equal to55), surface adsorption of PASP on calcite surface still plays an important role, and both acidic species attacks (H+, and HnLn-4, n = 1,2,3,4, attacking carbonate sites) and chelant attacks (L-4- and HnLn-4, n = 1,2, attacking calcium sites) affect the calcite dissolution. The dissolution of calcite in acidic PASP solutions represents the most complicated case.