The invention provides a method for generating over-driving data and a device thereof. The preparation method includes the following steps: (a) a reduced over-driving table and a preset weight value table are stored; (b) according to a previous picture element value and a current picture element value, a first reference value and a second reference value are searched from the reduced over-drivingtable; (c) according to the current picture element value, a first weighted value and a second weighted value are searched from the preset weight value table; (d) the first reference value, the second reference value, the first weighted value and the second weighted value are used for obtaining an over-driving data. The device comprises a memory unit, a reference value generation unit, a weightedvalue generation unit and a calculation unit. The method for generating over-driving data and the device can effectively reduce the size of the over-drive table, while the quality of an output picture can be maintained, thus providing a user with more convenience.