An object detection and tracking method and system are provided. The object detection and tracking method includes the following steps: (i) selecting one of a plurality of frames of a video as a current frame, (ii) searching in an object tracker searching area of the current frame to generate a current object tracker, (iii) searching in each auxiliary tracker searching area of the current frame to individually generate a current auxiliary tracker, (iv) when the current object tracker is located at a block different from the blocks located by the generated object trackers, generating a new auxiliary tracker at the central position of the current frame, and (v) repeating the above steps until all the frames have been processed.