A display controller capable of detecting data line similarity is provided. The display controller includes a buffer for temporarily storing a plurality of data lines of a target field, a data line similarity detector, coupled to the buffer, for detecting a similarity of each data line of the target field, a data line state recorder for recording the similarity of each data line of the target field, a de-interlacer coupled to the buffer, and a scaler coupled to the de-interlacer, wherein the de-interlacer selectively de-interlaces the target field according to the content stored in the data line state recorder in order to generate a de-interlaced output, and the scaler generates a scaling output according to the de-interlaced output.