You need to apply for a special visa at us consulate: returning

On the other hand, remaining outside the U.S. for more than one year does not mean you automatically lose your green card. If your absence was intended from the start to be only temporary -- for example, you left for vacation, but had a head injury and forget who you were for a year -- you may be able to argue to keep your permanent resident status. However, you may no longer use your green card as a U.S. entry document. You must have what is known as a reentry permit, or you must apply at a U.S. consulate for a special immigrant visa as a returning resident.
The Commuter Exception
Green card holders who commute to work in the U.S. from Canada or Mexico on a daily or seasonal basis may keep their cards even while actually living outside the country. USCIS will grant you commuter status if you advise them of your intention to live on the other side of the U.S. border.
Returning Resident Visas
If you stay outside the United States for more than one year and do not get a reentry permit (described below) before leaving, you must apply at a U.S. consulate abroad for a special immigrant visa as a returning resident. You must convince the consular officer that your absence was temporary and you never planned to abandon your U.S. residence.
You will have to show evidence that you were kept away longer than one year due to unforeseen circumstances. Such evidence might be a letter from a doctor showing that you or a family member had a medical problem.
Reentry Permits
If you hold a green card and know in advance that you must be outside the United States for more than one year, it's worth applying to USCIS for a reentry permit. This lets you to stay away for up to two years.
You should send in your application before leaving, and wait until you've been called in for your biometrics (fingerprinting) appointment. Use Form I-131, available on the USCIS website. Your reentry permit will serve as an entry document when you are ready to return.
Reentry permits cannot be renewed and can be applied for only inside the United States. If you want to stay away for more than two years, you must return briefly and apply for another reentry permit.

请您先登陆,再发跟帖!