Abstract: As a sensitive biological indicator, the Ephemeroptera, Plecoptera and Trichoptera (EPT) index is widely applied for bioassessment. To explore the spatial-temporal distribution characteristics and the key environmental influencing factors for the community index among different ecoregions in the Taizi River Basin, field work on the macroinvertebrate community and environmental factors was conducted in May (dry season) and August (rainy season), 2009, among the three aquatic ecoregions (AE) in the watershed. The results showed that the EPT richness and species composition were significantly different among the three AEs. The EPT richness in AE-Ⅰ was markedly higher than the other two regions. The only seasonal discrepancy was found in the richness of Trichoptera, which was significantly higher in the rainy season than in the dry season. The results of CCA showed that the key environmental factors affecting the EPT community in the AE-Ⅰ were electrical conductivity (EC) and water temperature (WT), whereas they were EC, sand contents, BOD₅, the total phosphorus (TP) and ammonia nitrogen (NH₃-N) in the other AEs. The PLR models were established to identify the correlation between species and environmental factors in each AE. The model for AE-Ⅱ had the highest interpretation ability which is approximate 0.60, followed by AE-Ⅰ (0.13-0.43) and AE-Ⅲ (0.13-0.53). The explanation of rainy season and the dry season suggested by the model were 0.33-0.78 and 0.43-0.71, respectively. The results of PLR also indicated that, with respect to the single model, the combined model which integrated different types of environmental factors had a better interpretation ability when explaining the spatial variation of EPT community in Taizi River Basin.