多谢，我也找到了官方的说法 https://www.help.cbp.gov/s/article/Article1287?language=en_US Traveling outside U.S. - Documents needed for Lawful Permanent Residents (LPR)/Green Card holders
Lawful Permanent Residents (LPR) of the United States must present a Permanent Resident Card ("Green Card", Form I-551) or a Reentry Permit. If you are an LPR unable to return to the United States within the travel validity period of the green card (1 year) or the validity of the Re-entry Permit (2 years), you may be eligible and can apply at the nearest U.S. Embassy or Consulate for a Returning Resident (SB-1) immigrant visa. United States LPRs do not need a passport to enter the United States as per 8 CFR 211.1(a), however, they may need a passport to enter another country. Please contact the embassy of the foreign country you will be traveling to for their requirements. While CBP does not require the passport as noted above, the airlines may have their own requirements, please check with your airlines prior to travel. Also, travel documents for LPRs do not need to be valid for any certain amount of time.Your LPR card only needs to be valid on the day that you are entering the United States. LPRs who are out of the United States for more than 180 days are subject to new immigrant inspection procedures as per 8 USC 1101. Foreign nationals who have applied for permanent residency may need to be approved for advance parole prior to traveling out of the United States. In order to be readmitted when traveling back to the United States. (H1, H4, L1, L2, K3, K4 or V2, V3 holders do not require advance parole to travel abroad after applying to adjust status. NOTE: U.S. Citizenship and Immigration Services now issues employment and travel authorization on a single card for certain applicants filing an Application to Register Permanent Residence or Adjust Status, Form I-485. The card looks similar to the current Employment Authorization Document but will include text that reads, "Serves as I-512 Advance Parole." A card with this text will serve as both an employment authorization and Advance Parole document. Article Number 000001287
多谢，在网上有看到说绿卡必须要6个月有效期。
网上信口开河的人很多 这种信息要去官方网站查
回美国 哪怕还剩一天都行。过期理论上也可以 但是航空公司不会让你上飞机。 6个月有效是针对拿绿卡去第三国免签 特别是拉美国家 哥伦比亚 哥斯达黎加 等 要求绿卡和护照都必须6个月有效 才能免签入境。
多谢，我也找到了官方的说法 https://www.help.cbp.gov/s/article/Article1287?language=en_US Traveling outside U.S. - Documents needed for Lawful Permanent Residents (LPR)/Green Card holders
Lawful Permanent Residents (LPR) of the United States must present a Permanent Resident Card ("Green Card", Form I-551) or a Reentry Permit. If you are an LPR unable to return to the United States within the travel validity period of the green card (1 year) or the validity of the Re-entry Permit (2 years), you may be eligible and can apply at the nearest U.S. Embassy or Consulate for a Returning Resident (SB-1) immigrant visa.
United States LPRs do not need a passport to enter the United States as per 8 CFR 211.1(a), however, they may need a passport to enter another country. Please contact the embassy of the foreign country you will be traveling to for their requirements.
While CBP does not require the passport as noted above, the airlines may have their own requirements, please check with your airlines prior to travel. Also, travel documents for LPRs do not need to be valid for any certain amount of time. Your LPR card only needs to be valid on the day that you are entering the United States. LPRs who are out of the United States for more than 180 days are subject to new immigrant inspection procedures as per 8 USC 1101.
Foreign nationals who have applied for permanent residency may need to be approved for advance parole prior to traveling out of the United States. In order to be readmitted when traveling back to the United States. (H1, H4, L1, L2, K3, K4 or V2, V3 holders do not require advance parole to travel abroad after applying to adjust status. NOTE: U.S. Citizenship and Immigration Services now issues employment and travel authorization on a single card for certain applicants filing an Application to Register Permanent Residence or Adjust Status, Form I-485. The card looks similar to the current Employment Authorization Document but will include text that reads, "Serves as I-512 Advance Parole." A card with this text will serve as both an employment authorization and Advance Parole document.
Article Number 000001287