I'm french in Australia with working holiday visa which expire in 1 month. Can I apply for a China Z visa in Australia?

You can try to apply for a China visa in Australia with this working holiday visa.

Even with less than 6 month of validity?

you need to provide the entry record for Australia as well for China visa application.

I just call the CVASC to know which document do I need to provide regarding to my application with a French passport according to what you all answer me (I can apply with WH Visa). but they just tell me that I can't apply because I don't have a 3 years visa...

What can I do? What are my option?

So, now you need to return to your home county and apply there for a work visa for China. Anyway, if possible, you can try to apply again in Hong Kong.