Why should I go to Australia to get married with my boyfriend, and come to China to get a marriage certificate, and then go to Australia to get a marriage certificate?

What you said is not clear. First of all, it is necessary to find out whether any of you hold an Australian passport. If you are all citizens of China, why did you get a marriage certificate in China and get married in Australia?

1。 As a citizen of China who has lived abroad for a long time, if he wants to get married, he only needs to go through the relevant formalities at the local consulate in China (I'm afraid tourists are not included), or his household registration is still in China, so he can go back to China to go through the marriage formalities.

2。 If one party is a foreign citizen or holds a foreign passport, the procedure will be more complicated. For example, if a China citizen wants to marry an Australian citizen in Australia, China must apply for the certificates needed to get married in Australia, usually including the single certificate (or divorce or widowhood certificate). It seems that all these must be handled in China, but the consulate doesn't. ), legal residence in Australia, etc. If you want to get married in China, then Australian citizens need to apply for a bachelor's degree and other relevant documents in Australia.

Your question is not clear. I don't know what kind of situation you are now.