Functionality of rangeland landscape determines the ability of ecosystem to conserve or lose vital resources such as water, soil and organic matter. Therefore, the functionality of rangeland is highly related to its vegetation cover. This study aimed to analyse the applicability of a Cover Directional Leakiness Index, CDLI, in rangeland functionality assessment of a Steppe zone, using satellite imagery in a case study in Soh region, Isfahan, Iran. This index was calculated based on a spectral index called Perpendicular Distance vegetation index, PD54, using green and red bands of Landsat TM 2009 data. The CDLI varies from 0 to 1 where a studied site is fully functional versus fully dysfunctional, respectively. The calculated CDLI for the study area was about 0.79 which indicates low functionality as its low plant cover percentage (<20%) can not capture and conserve resources. Statistical analysis also showed that relationships between CDLI and vegetation cover index was significant at the 95% confidence level. According to the results, the CDLI index can be used as a supplemetary tool to field methods for determining and assessing the functionality of Iran’s low-relief rangeland landscapes.