The present study aimed to study the diversity and density of the benthic fauna along the Inaouene wadi in relation to the variation of physicochemical parameters and heavy metals at six sampling stations representing the major part of the studied watercourses. The samples were taken during March and April 2019. The fauna recorded in this work consists of 2029 individuals corresponding to 39 families and 10 orders. The benthic population size showed that Oligochaetes, Diptera, Heteroptera, Trichoptera and Ephemeroptera are dominant. The diversity indices of Shannon and Weaver, and Piélou show that station S6 favors a better development of macroinvertebrates. This is confirmed by the values of physicochemical parameters and studied noble metals lord which shows that the stations S1, S3, S4 have poor water quality, compared to S6 and S5, the waters of which are of good quality, reflecting the self-purifying action of the watercourses between Wadi Amlil and Idriss I dam.