First, you need to know that there is a difference in procedures involved, depending on whenever you lost your card on U.S. territory or outside of the U.S. Therefore, we have divided the answer to how to replace your Green Card into two passages.
Losing a Green Card in the U.S.
If your Green Card is lost and it happened in the U.S., the process to replace your Green Card in this situation is quite simple. To do this, you also need to file Form I-90, Application to Replace Permanent Resident Card. You can file Form I-90 online or by mail.
Documentation required usually involves a photocopy of your original Green Card, a copy of another form of government-issued identification such as a driver’s license, or other evidence of your status and personal information.
Whether you have to travel abroad, and there is no way to postpone it, you have to call United States Citizenship and Immigration Services (USCIS) by using 1-800-375-5283 (TTY 800-767-1833) and request an I-551 stamp on your travel document. This stamp serves as proof of your permanent resident status and is valid for one year.