"Qist" is one of the key concepts in the holy Quran and it means the idea of "Justice". This idea is considerable in various fields of Humanities such as Politics, Economics, Laws and Social Sciences. Although Muslim scholars – such as philologists-have studied on the concept Qist and finally marked the semantic components "justice" and "right" for it, but since the concept justice have itself an opacity and its components is not clear, still a semantic study on this Quranic key concept is needed. The auther in this article intends that presents a semantic analysis of the Qurainc word "Qist", by using various theories in Semantics, like Syntagmantic Relations, Semantic Fields and Semantic Components, and also by using various methods in Historical Linguistics, like Etymology, Typology and Semitic Studies. In the first step, the semantic components of Qist discovers by using Etymology. in the next, by discovering the semantic fields of Qist in the holy Quran, Existing of this semantic components in the conext of verses will been measured. As a result, the word Qist have semantic components "law", "right" and "truth", and in the holy Quran used at the fields of laws, judgeship, transactios and justice in social acts.