For automatic detection of tire crown cord overlap defect, a detection method based on the crown X ray image was presented. Firstly, the gray cumulative projection curves that X-ray image was projected along different angles were obtained. Secondly, the local peak energy distribution of curves were calculated and the energy feature vector was constructed by the n largest peak energy values. Thirdly, the tire crown crack image was recognized by the maximum projection curve which could be distinguished through the energy feature vector by Support Vector Machine (SVM). Lastly, using the position inverse calculation, the tire crown crack was located. The experimental results demonstrate that the proposed approach was effective to detect the defects of tire crown which caused by tire cord overlap. The highest rate of correct detection can reach 97.7% in the 1000 crown images collected by the process of production.