Mites are the best representative of soil arthropods, because they are the most diverse in terms of ecological niche and behaviors. The first step in the biodiversity investigation is the study of soil mite fauna and identification of the species in each region. In order to determine soil mite fauna at Saman and Shahrekord districts several sampling programs were carried out and the results showed that the collected specimens belong to 12 families, 17 genera and 24 species . Multidentorhodacarus denticulates was reported from Iran for the second time. Abundance and biodiversity of mesostigmatid soil mites were calculated in eight sites at Saman and Shahrekord, each site including an orchard and a farmland. The biodiversity of mites was measured by several biodiversity indices and finally they were compared by the analysis of variance. The biodiversity index values calculated in different months showed that these indices usually were higher in warm months and in orchards than that of cold months and field crops. In the examined crop fields the diversity index values were lower at the harvesting times, probably due to soil disturbance by agricultural machinery. There was a significant difference in the Shannon-Wiener diversity index of mites among different land uses. The maximum and minimum values of this index were in almond orchard at site Saman code of almond/barley (1.40) and barley farm at Saman code of almond/barley (0.16), respectively. In almond orchard at Saman code of almond/barley, the Margalef species richness index was highest (1.78). In Saman, the maximum and minimum amounts of the Simpson index were in the vineyard (6.35) and the wheat field (1.97), respectively. Quantity of soil organic matter was maximum in the vineyard (2.12%) and minimum in the wheat at Shahrekord code of ulme/wheat (0.41). Based on the results, areas with highest soil organic matter had the highest number of soil mites. In this study, the regression line equations and correlation coefficient between the soil organic matter and biodiversity indices were also calculated. The coefficient of determination (R 2 =0.898) between soil organic matter and the Margalef species richness index was higher than other indices. The maximum and minimum coefficient of determination values between soil organic matter and the Shannon-Wiener index values and abundance of soil mite mesostigmata was 0.882 and 0.63, respectively. There was a weak correlation between soil organic matter and the Simpson index. Key words: Mesostigmata, Biodiversity, Richness, Simpson Index