Chomsky proposed that human being are born with an innate ability known as Language Acquisition Device, or LAD. The LAD was described as an imaginary \"black box\" existing somewhere in human brain. The \"black box\" is said to contain principles that are universal to all human languages. Children need access to the samples of a natural language to activate the LAD, which enable them to discover his language\u0027s structure by matching the innate knowledge of basic grammatical system to that particular language.Key: Chomsky referred to children’s innate ability to learn their native language as Language　 Acquisition Device (LAD). The LAD was described as an imaginary “black box” existing somewhere in the human brain. The “black box” is said to contain principles that are universal to all human languages. Children need access to the samples of a natural language to activate the LAD, which enables them to discover his language’s structure by matching the innate knowledge of basic grammatical system to that particular language.