It's said that...意为“据说……”，it 是形式主语，真正的主语是后面的that所引导的名词性从句，相当于somebody says that...其中It is said并不是有被动意义。类似的结构有：[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ p'Y,VD;j|br4FroG]

    It is reported that... 据报道……[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ jN-*9p:DHR N?,dTuFroG]

    It is believed/supposed that... 人们认为……[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ +[8b7xF"Y^3:Nmx2+FroG]

    It's known that... 众所周知…… 如：[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ # 2\]l^0?(%fx{`#FroG]

    It's said that Lantian Middle School is quite a good one. 据说蓝田中学是非常好的一所学校。[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ ^Cp+,)mMr[E ?CDW3FroG]