Objective To investigate the relationship between the expression of FAS/FASL and spermatogenesis in the contralateral testis after unilateral testicular torsion in puberty Sprague-Dawley rats. Methods Five groups of side testicular torsion adolescence SD rats model were established as follows:group A as control group, group B for testicular torsion group,group C for testicular torsion plus methylprednisolone group, D for reverse side testes excision group, and Group E testes excision plus methylprednisolone group for reverse side. SD rats were treated with testicular resection and/or injection of methylprednisolone after torsion for 24 h. The rats were executed at postoperative 1 month, and contralateral testes were collected for histopathological examination. Expression of FAS and FASL was analyzed quantitatively by immunohistochemistry with a computer pathological image analysis system. Each rat was evaluated with regard to endocrine parameters (follicle-stimulating hormone (FSH), luteinizing hormone ( LH) and testosterone ( T) by radioimmunoassay. Results Histopathological examination of the contralateral testes showed that either orchiectomy or orchiectomy plus methylprednisolone was more successful than no treatment. Fas/FasL protein in both control group and 4 experimental groups were expressed. B group showed more expression of FAS and FASL than that of the other groups. FSH, LH and T were normal in all cases. Conclusion Unilateral testicular torsion in puberty SD rats may result in higher expression of FAS and FASL, and accelerate germ cell apoptosis and subfertility. Methylprednisolone may decrease the expression of FAS and FASL and maintain spermatogenesis in the contralateral testis after the unilateral testicular torsion.