Pollution index has limitations in assessing the pollution risk of heavy metals in the carbonate-type tailings(i.e., carbonate-rich sulfide tailings). In this paper, the authors probed into this problem by investigating the carbonate-type tailings in the Huangshaping Pb-Zn ore district. The study included the modes of occurrence of such elements as Zn, Cd, Pb, Cu and As, which included tailings profile structure, distribution of total values of elements and water soluble fraction, combination of secondary cement/lepidocrocite and elements, and mobility(water extraction percentage) and pollution index of elements in the tailings. On such a basis, the authors have reached the following conclusions:① A layered(banded) structure has developed in the tailings, which exhibits the order of strong cementation layer/hardpan(moderate brown, oxidized/acidified) → weak cementation layer(yellowish brown, sub-oxidation) → sand-like layer(olive gray-gray green, weak/non oxidation) from the surface to the deep part of the tailings; in addition, the elements are concentrated in the hardpan and weak cementation layer; ② The cement in the tailings consists mainly of lepidocrocite. The difference of binding force between lepidocrocite and elements may affect the stability/mobility of elements in the tailings; ③ Due to the high mobility and pollution index, zinc and cadmium are the major pollution factors; therefore, pollutions of Zn and Cd should be especially prevented and controlled in the mining site. Arsenic is regarded as a minor pollution factor, as it possesses lower mobility despite its high pollution index. Lead and copper have less impact on the environment, because their mobility and pollution indices are low. In conclusion, the combinational analysis of the pollution index and the modes of occurrence of elements can help avoid the limitations of the use of the pollution index in assessing the pollution risk of heavy metals in the carbonate rich sulfide tailings.