The invention provides a tire defect detection method based on singular value decomposition. A to-be-detected image I containing n pixels is divided to n m*m image blocks; each image block Pi is converted to a column vector ci; column vectors corresponding to all image blocks are used to construct an image block matrix M; through sequentially calculating the ratio of adjacent two singular values, the rank r of the image block matrix M is determined; the former r maximum singular values of the image block matrix M and the corresponding left singular vectors and right singular vectors are used to reconstruct a low-rank approximation matrix Mr of the image block matrix M; each column vector in the low-rank approximation matrix Mr is converted to an image block; all image blocks P are used to reconstruct an approximate image Ir of the to-be-detected image I; hard threshold segmentation is carried out on a residual image I-Ir, a binary image Ib is obtained, and coordinates corresponding to a pixel with a gray value to be one in the image are the defect position. The detection method can position the specific defect position, missed detection and error detection caused by manual operation are avoided, and the defect detection accuracy is improved.