The Affon River is one of the important rivers of the Ouémé River whose benthic diversity remained unknown. The present study aims to make the relationship between macroinvertebrates and physico-chemical parameters to access water quality of the Affon River. The measurement of physico-chemical parameters (temperature, pH, conductivity, transparency, depth and TDS, dissolved oxygen, ammonium, nitrite and phosphate) and the sampling of macroinvertebrates using a Surber net were carried out during floods in eight stations. A principal component analysis (PCA) and canonical correspondence analysis (CCA) were used. The indices of Shannon, Piélou, Simpson, Hilsenhoff, EPT and EPT/Chironomidae were used to assess the level of water pollution. The study identified 9755 macroinvertebrates divided into 4 classes, 14 orders and 49 families. Pollution-sensitive families (14 families) that are organic pollution indicators, as well as pollution-tolerant families (Chironomidae, Limnaeidae, Bithynidae, Physidae) were captured. Chironomidae were the most predominant and abundant family (FO = 100%). The predominance of Chironomidae coupled with the rarity of the Ephemeroptera, Trichoptera and Plecoptera would reflect the poor quality of the Affon River waters. The principal components analysis yielded groups of associations: The first group of stations Taneka 2 and 3 characterized by high values of ammonium and phosphate; and low values of conductivity and TDS; the second group of Tanéka 1 and Kolokondé 1 stations with low values of pH, transparency, ammonium and phosphates; and the third group of stations Kolokondé 2, Kpébouko1, Kpébouko 2 and Affon marked by high values of conductivity, TDS, transparency, depth and temperature. The canonical correspondence analysis revealed a strong positive correlation between Nemou

This study focuses on the biodiversity of macroinvertebrates of the Affon River. To reach this goal, eight stations were sampled and physical parameters such as temperature, pH, conductivity, transparency, depth, total dissolved solids (TDS) and dissolved oxygen were measured. Chemical parameters such as ammonium nitrite and phosphate were measured in the laboratory. We identified 9755 macroinvertebrates belonging to 4 classes, 14 orders, and 49 families. Chironomidae were the most abundant family whereas other sensitive insect's orders such as Ephemeroptera, Trichoptera, and Plecoptera were rarely found, suggesting a poor water quality of the Affon River. The principal components analysis yielded three groups of stations: the first group (Tenéka 2 and 3) characterized by high values of ammonium and phosphate and low values of conductivity and TDS; the second group (Tanéka 1 and Kolokondé 1) with low values of pH, transparency, ammonium and phosphate; and the third group of stations (Kolokondé 2, Kpébouko1, Kpébouko 2, and Affon) marked by high values of conductivity, TDS, transparency, depth and temperature. This study is a crucial step for any management and monitoring of the Affon River.