Can a Chinese passport holder transit through Taiwan. They do have usa green card.

I would assume because you're only en transit (airside) on one ticket, there's no concern.

The residence permit for USA has no relevance for the authorities.

I don't know all the details but I know it's an issue that has it's own thread.

Taiwan transit ban on PRC citizens (ex-China)

I am no expert either, but according to my friends who hold PRC passports they have no problem transiting TPE with one exception: departing from the mainland and transiting in TPE. They say that they may be asked for a current Taiwan travel card (for individual) by Chinese immigration at the departure airport. No one is clear what would happen if you don't have it.

The card is issued by Chinese authorities and they have not been normally processing applications on the mainland since 2019, maybe 2018, when China banned individual travel to Taiwan. They do readily issue them in overseas consulates for overseas residents.

So before leaving the US, to be safe ask your friend to check with their nearest PRC consulate to see if they need a Taiwan travel card to enter or exit China on a flight to or from TPE. Don't wait until arriving in China.

They cannot transit through Taiwan from China (unless leaving from CKG/KHN/KMG). Going the other way is fine.

Do you know if a PRC passport holder with a Taiwan travel card can transit in TPE leaving China?

I know someone who says he did it earlier this year, but I am now wondering if it was "self connecting" on two separate tickets. I don't even know that you can issue a single ticket leaving China and transiting in TPE. I had one years ago, a Star Alliance RTW fare, and was told at CA check in at PVG that was an illegal routing. They eventually let me fly saying China immigration may stop me but they did not.

You might get a lecture at immigration entering China, but yes, it's fine.

Not unless they have a Chinese exit visa for entering Taiwan. This is usually only possible for Chinese citizens living in Taiwan (e.g., married to a Taiwanese spouse).

Technically right now the possible categories are

- (close) relative in Taiwan
- business
- education
- medical tourism (but this has been tightened I've heard)

only if the first flight is CA409