I am an Indonesian and will marry a Chinese next year in China. What documents should I prepare?

You should prepare single status certificate & birth certificate which should be translated into Chinese, notarised at your locla Notary Public, and then authenticated by the local Chinese embassy or consulate.

If you think of marrying in Australia, you can either contact Indonesian or China embassy(consulate) there for practical help. Anyway, I think it also will work. Congratulations and best wishes to you.