Disclose is a method for preparing a cathode material for a lithium secondary battery, the method comprising the steps of: preparing an amorphous silicon oxide; using the prepared silicon oxide as a starting material; and milling the amorphous silicon oxide, a lithium silicon oxide and a transition metal silicon oxide at a predetermined ratio, drying the milled material, and heat-treating the dried material in an atmosphere of inert gas, thereby preparing a lithium transition metal silicon oxide.