Documents should be notarized by a public notary.
The notarized documents should then be authenticated by the Department of Foreign Affairs and Trade, or its Office in States or Territories.
Note that if you send your documents via post, your application should be mailed to the DFAT’s offices in Melbourne or Sydney.
Apply for the documents authentication from the Chinese Embassy or relevant Consulate General where the documents were notarized (not authenticated), in accordance with consular regions. This must be done in person or via a service.
See the following page for an overview: http://au.china-embassy.org/eng/ls/Authentication/