ABSTRAK :rnrnEconomic system consists of 3 elements which are divided into subject, object and institution which organized both. One method that can be used to measure effectivity and performance of this economic system is by utilising economic development index. Among them, can be found, indices based on subject and institution approach. Meanwhile, one of the product based indices developed by The Centre for International Development (CID) Harvard University in 2010 is called Economic Complexity Index (ECI). This index utilises network theory analysing 2 types of conectivity; first, the concept of complexity and ubiquity which is the linkage between a country and its products. Second, the concept of product proximity which is the linkage among products itself. This article is trying to provide an introductory review about economic complexity index.