此句应改为:       Libei is one of the greatest poets that have ever lived in China.       因为定语从句的先行词是复数名词poets，因此要在从句中用复数。       

         一般说来，“one of + 复数名词” 结构的中心词是后面的复数名词，因而后面所接定语从句的先行词也是该复数名词。例如:       

      It was one of those trains which give you an understanding of eternity.         

那是使人懂得什么是永恒的那种火车之一。        

    但如果在one 前面加定冠词时，情况则有所不同，又如:        

    This is the one of the books on the subject that has ever been writing in Chinese.        这就是那本用汉语写的有关这个问题的书。        

     She is the only one of the few girls of my acquaintance that is acquainted with the old poet.         

    他是我认识的极少数的女子中与那个老诗人相识的唯一的一个。        

     这是由于加了定冠词以后，强调了the one,  the only one,  使他们成为后接定语从句的先行使，从而使从句谓语用了单数。