Abstract. Nusantara RW, Aspan A. 2017. Differentiation of soil organisms at different types of peatland in West Kalimantan,. Peatland conversion could threaten the soil organisms existence which is influenced by soil physical properties. The aim of this research was to analyze the changes in soil organisms of land-use due to the conversion of peatlands in West Kalimantan, Indonesia. The study was conducted in secondary peat forest (SPF), shrub (SB), oil palm plantation (OPP), and corn-field (CF) in Kubu Raya District of West Kalimantan. The stages in this study include observation of water-table depth, soil temperature and analysis of physical properties include bulk density, moisture, and porosity.The results indicated that a decline in colonies of bacteria and fungi in OPP than SPF, 50% and 53% respectively. The decline in the condition of affected water content decrease due to the land conversion of secondary forests into oil palm plantations (22.8%). Additionally characterized by conditions on the water-table depth was deeper and soil temperature was higher in OPP than SPF (16.8%). This condition was the opposite in CF, where both bacteria and fungi increased 53% and 33.3% respectively. The different conditions characterized by the water content, water-table depth, and bulk density even though the temperature was almost the same between OPP and CF.