此句型实质上是“主＋系＋表”结构。
其中it是人称代词，并无实意，指的是某种情况seems为系动词that / as if 引导表语从句。
一、It seems that....：表示：“看起来……”。
强调根据一定的事实所得出的一种接近于实际情况的判断，可以说表示事实。（可以转换成名词或代词+seem ＋动词不定式”句型，其意不变，如果动词不定式为to be ＋形容词时，to be往往省略。）
例：It seems that it is more difficult for women to get to the top of the company.妇女似乎更难提升到公司的最高职位。
It seems that no one knows what has happened in the park.(=No one seems to know what has happened in the park.)似乎没有人知道，在公园里发生了什么事。
二、It seems as if....：表示：“看起来……，似乎……” 表示“可能”
若从句表示的是很可能实现的事情，从句谓语用陈述语气若从句表示的是与事实相反的假设或实现的可能性很小的事情时，则从句谓语要用虚拟语气。
1、从句的谓语动词常用虚拟语气来表示：“所设想的事情不真实或不可能发生/存在”。
例：It seems as if she had read this novel.看来她好像看过这本小说。
It seems as if it were autumn.现在仿佛是秋天似的。
2、如果可能性很大则用陈述语气，或者句中的情况可能发生或可能被设想为真实，则仍然用陈述语气。
例：It seems as if our team is going to win.看来我们队要胜了。
It seems as if he has learned by heart a speech written by someone else.看来他像是背了一篇由别人写的演讲稿
