A method for manufacturing a nanostructured metal oxide calcinate suitable for biosensor through a procedure of redox reaction is disclosed in this invention. The nanostructured metal oxide calcinate is free of impurities and produced with better electrocatalytic activity and better conductivity. Thus, an electrode of biosensor can be modified via the nanostructured metal oxide calcinate. The method for manufacturing the nanostructured metal oxide calcinate includes: disposing a first metal material and a second metal material into a reaction slot and making the first metal material and the second metal material dissolved within a solvent to form a mixture, wherein the pH value of the mixture ranges between 0 to 7, the mixture performs a redox reaction process for obtaining a metal oxide material; and eventually calcining the metal oxide material for obtaining a nanostructured metal oxide calcinate.