ObjectiveTo explore the species distribution and constituent ratio of diatoms in main sections of urban district rivers where drowning occurs frequently in Chengdu.MethodsTotal 39 water samples from the sampling points of 5 rivers(Jinjiang, Jinniu, Qingyang, Wuhou and Chenghua districts)in Octo-ber 2014 were collected. The diatoms smear were made and the species distribution and constituent ratio of diatoms from the water samples were analyzed using biological microscope and acquisition system of digital microscope.ResultsTotal 21 species of diatoms were detected in main sections of urban district rivers in Chengdu. Significant differences in the dominant diatom species and proportions of the different rivers were observed, and there were different species existed in all sampling points of the upstream, midstream and downstream of the rivers.ConclusionThe database of species map, species distribution and constituent ratio of diatoms in main sections of urban district rivers in Chengdu are preliminarily es-tablished, which has special meaning for the analysis and evaluation of falling location inference using diatoms test in case investigation.