Abstarct: Oil contamination would cause environmental problems like air, water and soil pollution. Oil leakage and soil contamination make troubles for humans and other organisms. For remediation and reclamation of soil there are so many ways, but sometimes remediation isn't possible or not necessary. Changing in geotechnical parameters of contaminated soil is important issue for foundations, excavations and slopes. So researchers start testing on different types of soil to assess soils behavior with oil contaminations. Since there isn't any study on contaminated collapsible soil, in this study we want to test the collapse potential of these soils. At first for testing these soils 10 boxes of undisturbed samples have been taken from Kalale. Then undisturbed and remolded samples were caught from field samples. It's worth mentioning that remolded samples had the same void ratio as undisturbed samples. In order to assess the behavior of these soils, saturated and unsaturated test were done that unsaturated apparatus were assembled in Shahrood University. Samples were in different conditions of saturation. Saturated tests were carried out on clean soil with water as pore fluid and pure soil with gas-oil or lamp-oil as pore fluid third type of samples contaminated with gas-oil or lamp-oil with weight content and saturated with water. Content of contamination were 2%, 4%, 6%, 8%, 10% of dry weight of soil. Unsaturated Oedometer tests under constant vertical stress and varying matric suction were performed on a pure soil and a soil with 6% gas oil. The result showed that with disturbing loess soils collapse potential decreases even though the samples remolded in the same void ratio of undisturbed sample. Saturating the samples with gas oil and lamp oil disappear collapse potential and made it to a very slight value. Samples that contaminated with different gas oil and lamp oil contents haven't a specific decrease or increase of collapse potential with increase of oil content. Unsaturated tests for pure and gas oil contaminated soil showed that sample with contamination adsorb less water than pure soil and pure soil had a little more volume change with decreasing the suction.