From 20 August 1986 a person born in Australia acquired Australian citizenship by birth only if at least one parent was an Australian citizen or permanent resident.
http://www.jincao.com/fa/01/law01.17.htm
中華人民共和國國籍法
第五條 父母雙方或一方為中國公民,本人出生在外國,具有中國國籍;但父母一方為中國公民為並定居在外國,本人出生時即具有外國國籍的,不具有中國國籍。