Abstract: A mathematical model of steady state gas release flow rate in long distance pipeline is given by use of computational fluid mechanics. It is found that the hole model is suitable to gas release through a small hole, while pipe model is suitable to the gas release through a hole corresponding to the complete breaking of the pipe. A new model is proposed for the hole that lies between the small hole diameter and pipe diameter. The results show that the new model covers all the possible hole diameters. This new model is a combination of hole model and pipe model. When the hole diameter is relatively small, the results given by the new model is the same as that of the hole model; when the hole diameter is equal to the pipe diameter, the new model predicts the same results as that of pipe model. It is the new model that should be used when the hole diameter is larger than small hole diameter, but smaller than the pipe diameter.