Diets and digestive tract histology of loach fish Turcinoemacheilus bahaii (Esmaeili, Sayyadzadeh, Ö zulug, Geiger & Freyhof, 2014) (Nemacheilidae) were studied in Zayandeh Roud River. Fishes were cached seasonally by two layers gillnet (with an outer mesh of 10 mm and inner mesh of 5 mm) in Deme region of Chaharmahal and Bakhtiyari province through one year (2013-2014). On each sampling date, the macrobenthos were also taken by a Surber sampler (size 25*25 cm with mesh 500 μ ). In order to evaluate diet of loach fish, the contents of gastrointestinal were studied and showed that this species mainly fed on macrobenthos in Zayandeh Roud River. The dominant macrobenthos group during present study was included Chironomidae, Hydropschidae, Gamaridae and Baetidae which showed a noticeable overlap with the diet of T. bahaii. Chironomidae and Baetidae (composing %82 of total frequency) were used as the most abundant prey by loach fish. The average of Relative Gut length (RLG) (0. 46± 0. 04 mean± SD) also confirms that the species was classified as carnivore. The digestive tract in the species was included the esophagus, stomach and intestine and the histological characteristics revealed that the wall of digestive tract is composed of the tunica mucosa, submucosa, muscularis and serosa. The tunica mucosa had simple columnar cells that in associated with goblet cells in intestine. The overall results of studying on benthos in the river, contents of the digestive tract and histology of digestive tract indicated that the diet and structure of digestive tract of loach fish were based on the different food items which were recommended by natural habitat.