Aquatic insects were used in water quality assessment of some branches of Greater Zab River within Erbil city Kurdistan region of Iraq. The benthic macroinvertebrates' samples collected at three sites during periods extended from April to November 2014 at monthly intervals. Generally, the sample of aquatic insect collected from studied sites contained at least 662 taxa, a total 25 species representing 9 families from 4 orders were identified, 18 of them were recorded for the first time in Iraq. From the site one a total of 172 taxa of aquatic insects were collected which belong to three orders, six families and fourteen species. Site two contained 187 taxa representing four orders, seven families and twenty species. Meanwhile, at the site three 176 taxa were collected in which belong to three orders, seven families and fourteen species. According to Shannon-Weiner index, species diversity ranged from 2.00 to 2.26 bits/ind. The highest diversity value recorded at site 1. While, the minimum diversity recorded at site 3. According to Jaccard similarity index the highest percentage of similarity occurred between sites 1 and 2and the low similarity observed between sites 2 and 3. Biotic Index (BI) used to assessing level of organic pollution of studied sites, the result showed that all the sites were enriched with organic pollution.