Whether there is a risk of shale oil leakage along the depleted wells or multi-level geological fractures during in situ oil shale mining was predicted using the geological data from the Songliao Basin and survey wells in Fuyu county of Jilin province, China. The simulation results obtained employing the Transport of Unsaturated Groundwater and Heat 2 (TOUGH2) software indicate that oil leakage along depleted wells would entail greater risks to the upper aquifer, while the leakage along multi-level geological fractures would involve higher risks to the lower aquifer close to the shale beds. The distributions of shale oil saturation under the original and 1.3-fold formation pressures are slightly different, and the pollution halo somewhat increased only in an aquifer 40-50 m underground. The shale oil saturation in the leaking channel may be 0 during the leaking process.