The invention relates to a memory cell of a resistive random access memory (RRAM) and a preparation method thereof. The memory cell comprises an insulating substrate; a first electrode is arranged on the surface of the insulating substrate; the surface of the first electrode is provided with an intermediate layer manufactured by the materials with resistance switching properties and the surface of the intermediate layer is provided with a second electrode. The memory cell is characterized in that the intermediate layer is formed by diamond-like carbon films. Compared with the prior art, the invention has the advantages that the intermediate layer does not adopt oxide materials but diamond-like carbon films; the RRAM of such a structure shows excellent property of switching from high resistance state to low resistance state and memory property under continuous sweep driving of DC voltage; the difference between the high and low resistance states can be more than 10<2> times; in the process of continuous 100 times cycling of high and low resistance states, the resistance values of the high and low resistance states show good stability; set voltage and reset voltage show good stability; the properties show that the invention has potential application value in the field of non-volatile memory devices.