Knowledge-intensive Business Service or KIBS is undoubtedly proved to be the activest section and innovation power in modern service industry. Although the systematic studies of KIBS in western academe can be traced back to the 90's of the 20th Century. However, there is still no accordant definition of KIBS existed at present because of the effect of different reasons. And this becomes the biggest obstacle for further investigation. In this paper, it reveals the dynamic features of the concept of KIBS and proposes the definition of KIBS which is suitable for currently national condition of China by collecting and sorting out the obtained data of KIBS systematically as well as comparative analyses.