“It is known that Chinese people are smart.” 中的It 指代that Chinese people are smart.it 不是只能指代一个名词吗？SAT作文中让这么用吗？it 不只是指代一个名词。it可以指代天气、距离和时间；it可以做形式主语；it可以做形式宾语。
“It is known that Chinese people are smart.” 中的It作形式主语， 指代that Chinese people are smart这个真正的主语。