A memristor and a preparation method thereof are provided. The memristor includes at least one memristive unit, each of the at least one memristive unit includes a transistor and at least one memristive component, the transistor includes a source electrode and a drain electrode; and each of the at least one memristive component includes a first electrode, a resistive layer, a second electrode, and a passivation layer, the first electrode is electrically connected with the source electrode or the drain electrode; the resistive layer is provided between the first electrode and the second electrode; and the passivation layer at least covers a sidewall of the resistive layer.