Interleukin-6 receptor (IL-6R) is a member of the hematopoietin receptor superfamily which has its common conservative structure “the cytokine binding domain (CBD)”. CBD is the functional domain of the extracellular region of IL-6R, because only this domain of IL-6R is responsible for IL-6-binding and for IL-6 signal transduction through gp130. It is proposed that the β-sheets folding motif of the IL-6R CBD is very similar to that seen in the crystal structure of human growth hormone receptor (hGH-R), which also belongs to the cytokine receptor family, and CD4. By means of computer-guided homology modeling techniques, the three-dimensional (3D) structures of hGH-R and CD₄ were used as template protein to predict the 3D-structure of the functional domain (residue 106～322) of hIL-6R. The characteristics of the conservative structure-conformation in CBD of hIL-6R were described. The model may provide for the interpretation of the results obtained with introducing site-directed mutation into soluble IL-6R and the 3D-quantitative analysis on the structure-function relationship of IL-6R functional domain.