It’s great significant for rectangular products factories to detect the maximum inscribed rectangular of target objects. The traditional method is artificial, with some shortages such as strong subjectivity, low efficiency and poor accuracy etc. In this paper, the traversing and center diffusion methods were utilized to detect the maximum inscribed rectangle of target objects-based on image processing, then on the basis, a new method was proposed. The experimental results showed that the traversing was strong robustness to noise, but was sensitive to the concave objects, the applicability of center diffusion was better, but the detection accuracy was lower; while the traversal center diffusion method revealed stronger robustness, and had more than 90% accuracy. Thus the proposed detection method in the work is effective for improving maximum inscribed rectangle of the object.