Abstract: In this paper,ultrastruscture of pigment gallstones after treatment with different solvents were obtained. Relative metal contents in the treated pigment gallstones were determined by EDS and the C H,N contents were also analyzed. By comparison of ultrastructure and elemental contents,it is suggested that the bilirubin and metal ions,in especial,calcium and other divalent metal ions,form bilirubinate or coordination compounds whilch then chelate with proteogly can to form macromolecular complexes,this the main reason of pigment gallstone difficult to be dissolved.