X-ray photoelectron spectroscopy (XPS) technique was used to study the coordination forms and transformation characteristics of P on goethite surfaces at different pH. The results showed that the chemical forms of P on goethite surfaces changed from the dominance of monoradical ligands to that of biradical ones with increasing pH of the solutions. For a given P concentration, increasing the pH of suspension could cause a faster transformation of monoradical ligands of P to the biradical ones on goethite surfaces, while lowering the pH the biradical ligands converted slowly to the monoradical ones. By influencing types of phosphate ions in the solution, pH affected the coordination forms of P on goethite surfaces. The dissociation and association of protons of the sorbed P caused by pH changes were considered as a major reason leading to the transformation of the coordination forms of P on the surfaces. The stability of biradical ligands of P was greater than that of monoradical ones. and the possible reasons were disscussed in paper.