A flow controllable epoxy resin prepreg and a preparation method thereof are disclosed. The preparation method comprises the following steps: individually preparing an epoxy resin component, a flow control component, and a curing component, adding the epoxy resin component and the curing component into the flow control component to prepare a flow controllable epoxy resin system with a viscosity more than 4 Pa.s, and finally compounding the system with an enhancing material so as to obtain the flow controllable expoxy resin prepreg; wherein the epoxy resin component can be single epoxy resin or a composition of multiple epoxy resins and accounts for 10 to 90% of the total weight of the system; the flow control component is a prepolymer or mixer of an epoxy resin modifier and epoxy resin and accounts for 5 to 60% of the total weight of the system, and the curing component is composed a single curing agent or a mixture of multiple curing agents or curing agents and promoters, and accounts for 2 to 30% of the total weight of the system. Through the provided flow controllable epoxy resin prepreg, the control modes of feeding pressurization and zero rubber absorption in the autoclave moulding engineering can be achieved, and thus the product quality is improved.