The invention discloses a capacitance-free dynamic random access memory structure and a preparation method thereof. Under the premise that the capacitance-free dynamic random access memory structure meets high voltage leakage requirements for a high impact ionization rate, the electrical thickness of a gate medium in a source drain junction area is increased via adoption of different gate medium materials or gate medium thicknesses near the area, an electric field in the vertical direction is reduced effectively. Meanwhile, a thin oxidation layer or a high K material is adopted in the central area of a channel, the gate control capability is improved, and the short channel effect is inhibited. By adopting the structure, the degradation of the gate medium can be inhibited effectively, the reliability (durability) of a storage unit can be improved, the scaling-down of a device can be facilitated, and the complex process for the capacitance structure in the conventional 1T1C structure can be avoided completely in the capacitance-free structure. The adopted manufacturing process is completely compatible with the conventional logic process, and the high-density three-dimensional process integration can also be facilitated.