Abstract: [Objective] The FSH33-53 peptide binds to its receptor FSHR and activates the downstream signal as a FSH functional peptide.However, its specific binding position on the receptor is unclear.The aim of this study is to elucidate the binding region of the FSH33-53 peptide on the receptor FSHR in the hope of providing a basis for FSH-based vaccine design.[Method]The extracellular domain(ECD)and leucine-rich repeat (LRR) of follicle-stimulating hormone receptor was amplified by polymerase chain reaction (PCR) and constructed recombinant plasmids pET22b-FSHR-ECD and pET22b-FSHR-LRR.Protein FSHR-ECD and FSHR-LRR were obtained by expression and purification.FSHR9-30-KLH.was obtained by peptide synthesis, and binding and affinity of receptor fragments with FSH33-53 peptide were detected by ELISA method.[Result]The proteins FSHR-ECD and FSHR-LRR were successfully expressed and purified and their relative molecular mass (MR) was 43 and 32kda., respectively.When the receptor was 0.5 μg / mL and the ligand was 2.5 μg / mL, the three proteins were bound to the FSH33-53 peptide.The affinity of ELISA to detect the ligand and ligand was 0.21 × 10-6, 0.45 × 10-6 and 0.056 × 10-6 mol / L, respectively.[Conclusion]The binding of LRR fragment to FSH33-53 peptide is stronger than that of the other two fragments.