The present invention discloses a novel polypeptide, a steroid dehydrogenase 34, the polynucleotide encoding the polypeptide and the method for producing the polypetide by DNA recombinant technology. The invention also discloses the uses of the polypeptide in methods for tresting various diseases, such as steroid hormone dysbolismus disease, such as sex dysgenopathy, some endocrine and metabolic syndrome, viarous tumors of human reproductive system, bile acid dysbolismus, etc. The invention also discloses the agonists against the polypeptide and the therapeutic action thereof. The invention also discloses the uses of the polynucleotide encoding the novel steroid dehydrogenase 34.