My girlfriend got an Australian green card and plans to go back to China to marry me next year. How do I apply for an immigrant visa?

After your girlfriend gets a green card, she can apply for a spouse immigrant visa when she gets your marriage certificate back home, and then wait for a few months in China and the visa will pass in a flash.

If you want to go there faster, if you have a good work and economic background, you can apply for a visit visa first, and then apply for spouse immigration there, so that you can be together earlier.

It is important to keep the proof of your relationship, such as chat records, telephone lists, air tickets, accommodation documents and so on. As long as your relationship is true, the visa problem is not big.