The aim of this study is to evaluate the effect of slop on root system characteristics of Q. castaneifolia. For this purpose, an experiment was conducted in the nursery of Forestry and Forest Economics department, Natural Resources faculty, University of Tehran with three treatment including flat area, area with 25 percent slope, and area with 45 percent slope with three replicates for each treatment. After preparing seeds, they were grown in pre-prepared plots. Seeds were cultivated after germination, in four periods (96, 124, 152, and 201 days). In each period, seven seedlings were selected randomly from each treatment and extracted carefully from soil. The characteristics of root system like number of roots, root length and root tensile strength were recorded. The results of the ANOVA showed that the slope had a significant effect on the number of the roots and the highest number was related to the flat treatment and the lowest was belonged to the treatment with 45 percent slope. While the maximum total length of the roots related to the 45 percent slope. The results showed that tensile strength decreased with increasing root diameter which the relation was power-law regression. The various growth periods had not a significant effect on tensile strength, however, root diameter as a covariate factor was significant.