Stealing oil by drilling hole brings great harm, including the oil loss, the negative influence on normal pipeline operation and risks of potential explosion, leakage and environmental pollution. At present, many researchers aim to identify the problems and have put forward some preventive measures, but few focus on the calculation of the loss. The transient hydraulic properties of the whole pipeline system during the process of oil theft by hole drilling is analyzed. Considering boundary conditions of the oil-stealing point, diameter-changing point, batch interface and valves, the model is established. Based on the pressure, flow rate and temperature, the transient and accumulated volume of stolen oil are given. The results show that: (1) the orifice free flow is different from short-pipe out flow, therefore the valves friction, the friction of the short oil-stealing pipe and the inside pressure of the oil-stealing tankers should be taken into in calculation; (2) The parameters influencing the amount of oil stolen can be ranked from large to small, namely the size of orifice, the pressure, flow rate and temperature; (3) The model has relatively better accuracy when the flow rate is lower, the pressure is higher and the pressure fluctuation is higher.