The invention belongs to the preparation technique of separation membranes as well as the field of novel materials, relates to a carbon membrane preparation method for oil-water separation, and particularly relates to a carbon membrane for phenolic resin-petroleum coke based oil-water separation as well as a preparation method thereof. The preparation method of the carbon membrane comprises the following steps: pretreating a precursor material which is a mixture of phenolic resin and petroleum coke, preparing powder, mixing and molding, pre-oxidizing and carbonizing so as to obtain the carbon membrane. The invention provides the novel and cheap carbon membrane precursor material which is the mixture of phenolic resin and petroleum coke as well as the carbon membrane prepared from the mixture of phenolic resin and petroleum coke for separating oil-stain-containing water. The problems of high price of a common carbon membrane precursor material, poor carbon membrane liquid separation performance, complex preparation technology and the like are solved.