Aim: To detect the anti-follicle-stimulating hormone (FSH) antibody in idiopathic infertile patients and fertile subjects in order to determine the role of this antibody in patients with spermatogenic dysfunction. Methods: The anti-FSH antibody in serum was detected by an enzyme-linked immunosorbent assay (ELISA). The functional and structural integrity of the sperm membrane was evaluated with hypo-osmotic swelling (HOS) test and the ultrastructure of the spermatozoa was investigated by transmission electron microscopy (TEM). Results: The extent of positive FSH antibody in the patients with oligozoospermia and/or asthenozoospermia was significantly higher than that in the fertile subjects and infertile patients with normal sperm concentration and motility, but it was significantly lower than that in the patients with azoospermia. The extent of anti-FSH antibody in the patients with azoospermia was significantly greater than that in patients with oligospermia and/or asthenospermia, infertile people with normal sperm density and motility and fertile people. The hypo-osmotic swelling test showed that the percentage of HOS-positive spermatozoa (swollen) was 45.1% ± 3.5% in the FSH antibody-positive group and 59.1% ± 6.2% in the FSH antibody-negative control group. The percentage of functional membrane damage to spermatozoa was significantly higher in the anti-FSH antibody-positive group than in the control group. TEM showed that the outer acrosomal membrane was located far from the nucleus, and detachment of the acrosome was found in the FSH autoantibody-positive group. Conclusion:These data suggest that the presence of anti-FSH antibody is strongly correlated with the sperm quantity and quality in idiopathic male infertility. Anti-FSH antibody may be an important factor causing spermatogenic dysfunction and infertility.