I have applied to immigrate to the United States, but I want to go again two years later, is that ok?

If you have obtained a visa, you must enter the country within the validity period of the visa, otherwise the visa will be invalid and you should apply again. You can enter the country first, get a green card, apply for re-entry permit and live in China for 2 years.

If there is no face-to-face interview, NVC can postpone each step of submitting materials by no more than 1 year.