Abstract: Joseph H.Greenberg’s research is centered on comparison linguistics theory, and based on methodology of multilateral comparison. He used this way to classify the languages over the world. First, he classified African languages into four groups; then he turned to the other languages and proposed relevant hypotheses, such as, Indo-Pacific hypothesis, Amerind hypothesis, Eurasiatic hypothesis. But his methodology is not suitable for all the languages, at the same time its objectivity is suspicious, because it’s hard to prove the languages involved are genetically related in this way.