1. A blur detection method of images, comprising steps: generating a reference image having a plurality of blocks; identifying a plurality of first blocks from the plurality of blocks, wherein an in-focus area is defined by the plurality of first blocks; generating a test image having a plurality of test blocks corresponding to the plurality of blocks of the reference image; identifying a plurality of second blocks from the plurality of test blocks that correspond to the plurality of first blocks in the in-focus area; and executing a determination procedure and generating a determination result based on information from the plurality of second blocks and the plurality of first blocks, and when the determination result meets a predetermined condition, determining the test image as a blurred image.