Abstract: In order to study the influence of the volume fraction of oil vapor on the explosion, experimental study and numerical simulation were combined to study the development mechanism of oil vapor explosion in oil pipelines. It is shown that the volume fraction of oil vapor is an important factor affecting the degree of oil vapor explosion. Besides, the maximum pressure of vapor explosion of crude oil is related to the initial vdume fraction of oil vapor. When the volume fraction of oil vapor is 5.51%-7.06%, the higher the vdume fraction of oil vapor is, the greater the explosion pressure is. When it is 7.06%, the explosion pressure is the highest. And when it exceeds 7.06%, the maximum explosion pressure decreases with the increase of the volume fraction of oil vapor. The research results reveal the explosion and spread laws of oil vapor in oil pipelines and they can be used as the guidance to reduce pipeline explosion accidents.