Abstract: Astragalus gossypinus Fischer with wide distribution in Iran belongs to the genus Astragalus (Fabaceae). According to existing references and information, individuals of this species are present in many stations with different ecological conditions. This study carried out for determination and discrimination of intraspecific diversity of Astragalus gossypinus by Eco-phytosociological method from west of Iran. In this method, the principle of data collecting and analyzing based on floristical composition (as floristical markers) of each Endogenous milieu (as the unit of study in Eco-phytosociological method). In this order, application of Endogenous milieu (special station) for data collecting and then their analyzing permit us only determine existence of inter and intraspecific diversity. Then for determinating kind and level of intraspecific diversity (Ecophene, Chemotype, Cytotype, Ecotype …), can use other studies such as: morphological, anatomical, phytochemical, cytological and etc. In this survey, 29 special stations were studied and 195 species distinguished as companions for Astragalus gossypinus. Then floristic-ecologic data collected from each 29 special stations and analyzed by Anaphyto software (F.C.A, A.H.C, B.O, Marquag methods). Comparison of obtained results on multiple coordinate axes from F.C.A method with results from B.O, Marquag and A.H.C methods led to determination of 7 main groups of Endogenous milieus (special station). Flavonoid analyses were used for determinating kind and level of intraspecific diversity in 7 discriminated groups. Leaves flavonoid components of all collected individuals of Astragalus gossypinus were investigated by TLC method. Obtained data from flavonoid survey analyzed by SPSS and MVSP package with WARD and UPGMA methods. Finally, the results of flavonoid studies confirmed the same 7 groups that identified by floristical composition study and showed intraspecific diversity in chemotype level. So according to these results, we can introduce 7 chemotypes for Astragalus gossypinus from west of Iran. These chemotypes exist in different stations with various ecological conditions.