Sri Lankan lives in Australia, have my own business in Australia

Dear sir/madam, I'm Yapa who lives in Australia, I have my own business in Australia, I'm planning to go china in this month, I have been last year as well, but my passport will expire within 4 months, and I have all the relevant document including government invitation, if I come to sri lanka and renew my passport can I get my visa to china? how long does it take? please let me know.
Regards
Yapa