The aim of this study was to investigate the ecological factors affecting the distribution of four Trifolium repense, T. pratense, T. micranthum and T. compestre species in Fandoghlou rangelands of Namin county in Ardabil province. Sampling was conducted in six sites with the presence and absence of species at random. Topographic, climatic, land cover and density of selected species were recorded. From each transect, soil samples were taken from the root activity depth the parameters of acidity, electrical conductivity, soil texture, lime, calcium, magnesium, sodium, phosphorus, potassium, organic matter, propagated clay and soil moisture content were measured. A significant difference was observed between the environmental factors on presence and absence of studied species by one-way ANOVA and comparison of the mean of the measured characteristics with Duncan test. To determine the importance of the variables in different sites and the species distribution, Linear Discriminant Analysis (LDA) was used. Results showed that there were significant different between the factors of electrical conductivity, slope, sodium, organic matter (p<0.01) and factors of elevation, rainfall, temperature, acidity, potassium, phosphorus, clay, silt, dispersible clay and bare soil (p<0.05) in sites of presence and absence of species. According to the results of the LDA, four functions were justified as 78.50, 15.60, 5.80, 0.10 %, respectively and totally 100% of the total variance of the data were justified. Four factors (temperature, electrical conductivity, potassium and clay) were identified as the most important factors in the distribution of the T. repense, T. pratense, T. micranthum, T. compestre species.