The aim of this study was conducted to investigate the effect of 25 years old exclosure on the function of aerial and underground organs of Trifolium pratense since may to july of 2017. Three sites inside and three outside of the exclosure were selected in the rangelands in Shoghaldare- Namin rangelands, Ardabil. Three transects with the length of 100 meters were established in each site and from 10 plots of 1 m2 vegetation characteristics including total production, canopy percentage and forbs canopy were estimated. In order to select T. pratense stand and measure the selected parameters (to study the effect of exclosure on the function of different organs of T. pratense), in addition to previous transects, in each site was randomly established 3 transect of 50 meters. Along each transect, 10 random points and in each point the nearest plant was selected. Length of root, stem, inflorescence, plant height and basal diameter of T. pratense were recorded. Moreover, the inflorescences, stems and roots of the selected T. pratense were cut and after air-drying, they were weighed with a precision scale. Results showed that the total production in the exclosure (2413/06 kg/ha) has significant difference (p < 0/01) with the outside of exclosure (963/84 kg/ha). The production of T. pratense inside exclosure (99.83 kg/ha) has also significant difference (p < 0/01) with outside the exclosure (22.75 kg/ha). Interaction of exclosure and elevation has significant effect on canopy cover (forbs and total), number of inflorescences, basal diameter, weight of plant organs (p < 0/01) and recovery effort (p < 0/05).