Steroid　5alpha-reductase　of　human　is　an　enzyme　in　the　biosynthetic　pathway　from　testosterone　(T)　to　dihydrotestosterone　(DHT).　Up　to　now,　no　crystal　structure　of　this　enzyme　has　been　reported.　However,　knowledge　of　the　tertiary　structure　and　possible　active　sites　is　essential　for　understanding　the　catalysis　mechanism　and　for　the　design　of　inhibitors.　A　model　with　putative　active　sites　has　been　created　and　evaluated　by　using　homology　modeling　and　molecular　docking　techniques　based　on　the　bioinformatics　knowledge.　The　homology　model　is　optimized　in　Swiss　PDB　Viewer　with　MM　method　and　substrate　structures　before　docking　are　also　optimized　on　HF/6-31G.　The　active　site　for　the　docking　of　NADP,　T,　DHT　and　Finasteride　is　located　near　the　N-terminus　of　enzyme.　Four　active　amino　acids　in　the　active　site　are　identified　as　Ala26,　Arg53,　Arg176　and　Lys177.　Reaction　procedure,　binding　pattern　of　active　sites,　the　types　of　weak　interaction　and　so　on　are　also　discussed.