To reflect the importance level of the different regions of prints and increase the print defects detection accuracy, a method of print defects detection was proposed based on sub-region and grading. Depending on the characteristics and importance of the detection area, prints were divided into different areas to extracted foreground and different detection levels were set. The print defects were identified according to human vision characteristics, and then the characteristics of extracted were defects analyzed. The method of sub-region defects detection can be implemented at the same time in different areas. It was superior to the method of non-subregion detection in the aspects of detection time consuming, detection accuracy rate and false detection rate. The method of print defects detection based on sub-region can well meet the needs of printing quality detection and improve the accuracy and efficiency of the print defects detection.