八十多歲的老父母 都有綠卡很多年。今年底想回中國。 我現在想著手辦理回美證：
1）是到哪裏下載131 ， 還是必須打印出來 ， 父母分別填好 ，寄給移民局嗎？
-Yes, they only can file the application by mail, not online. Check this link:
Application for Travel Documents, Parole Documents, and Arrival/Departure Records | USCIS
2） 寄出去以後，拿不到回美證也可以回國嗎？
-Yes. Your parents can leave US after they receive the I-131 receipt notice. Because they are more than 79 years old, they don't need to do the biometrics, but need to provide two their passport style photographs with the I-131 filing.
等回美證寄過來再給他們送到中國？
-Yes; or ask USCIS to send it to the US Consulate in China and then, they can pick it up at the US Consulate (you need to indicate it in the I-131 if they want to pick it up at the US Consulate).
謝謝八老師的幫助。
