Abstract Many natural fires occur in arid and semi arid rangelands that may result in destruction of desirable forage and also erosion of valuable rangeland's soil which eventually will lead to great environmental and financial losses. To study the effects of fire on soil physical and chemical properties, a research project was defined and carried out in semi steppe rangelands of Kordan located in southern Alborz Mountain north east of Karaj city. A randomized completely block design was used with two treatments (control and burned rangelands) and 15 replications in year 2008. Soils of the studied area (control and burned rangelands) were examined using sampling in the first spring season after fire was occurred. In each quadrate, percentage of canopy cover was measured. Statistical analysis was performed through factorial experimental design and means comparisons were done by Duncan's test. According to the results of soil analysis, amount of total N, absorbable phosphorous, absorbable calcium and soil organic carbon decreased after the fire. Magnesium absorbable, Cation exchange capacity and percentage of clay increased after the fire. Fire also had no significant effects on the percentage of sand, silt and soil bulk density.