http://www.border.gov.au/Trav/Citi/pathways-processes/application-options/migrant-with-permanent-residence/eligibility
To become an Australian citizen you need to meet certain requirements. For most applicants these include that you:
are a permanent resident at time of application and time of decision
meet the residence requirements
are of good character
have a competent knowledge of English
intend to reside or maintain a close and continuing association with Australia
have an adequate knowledge of the responsibilities and privileges of Australian citizenship.
If you are 60 years of age or over you are not required to sit the citizenship test.
General residence requirement
On 20 April 2017 the Australian Government announced that it would be strengthening the requirements to become an Australian citizen. This included increasing the general residence requirement, which means an applicant for Australian citizenship will need to demonstrate a minimum of four years permanent residence immediately prior to their application for citizenship.
Subject to the passage of legislation required to enact some of the measures, the changes will come into effect, and apply to applications made from the date of the Government's announcement on 20 April 2017.
The changes will not apply to applications made before 20 April 2017. The current rules will apply to applications made before 20 April 2017.
Under some circumstances you might be eligible to apply for a variation to the residence requirement or be eligible under the special residence requirement.
Calculate your permanent residency
If you were granted a permanent resident visa before you arrived in Australia, your permanent residence date is the date that you arrived in Australia on that visa.
If you were granted a permanent resident visa after you arrived in Australia, your permanent residence date will be the date that the visa was granted.
Children
You can include children under 16 years of age in your citizenship application if they are permanent residents.
Children under 16 years of age do not need to meet the residence requirements.
More information is available about children who are 16 and 17 years of age.