this work, the affinity of Fe2+ and Zn2+ for Im-SH group were investigated in the electrolyte solution of FeCl2 and ZnCl2 using quartz crystal analyzer (QCA). Imidazolyl-Alkanethiol (lm-SH) was coated on a side of quartz crystal electrode by the process of self-assembly. The result shows that the reaction of Zn2+ for Im-SH film is stronger them that of Fe2+. and the substitution reaction rises on (Im-SH)-Fe2+ film in the electrolyte solution of ZnCl2, whereas the (Im-SH)-Zn2+ film is stable in the electrolyte solution of FeCl2.