在irs网站上:http://www.irs.gov/taxtopics/tc851.html 开始说好像累计: To satisfy the 183 days requirement, count all of the days you were present in the current year, and one-third of the days you were present in the first year before the current year, and one-sixth of the days you were present in the second year before the current year. 但是又说: Even if you meet the substantial presence test, you can be treated as a nonresident alien if you are present in the United States for fewer than 183 days during the current calendar year, you maintain a tax home in a foreign country during the year, and you have a closer connection to that country than to the United States. 如果第二点是必须要要求的,那么开始说的累积不是完全没有用吗?