Objective To investigate the value of MRI in the diagnosis of adult osteonecrosis of the femoral head. Methods The clinical data and imaging data of 53 patients with femoral head necrosis admitted from July 2014 to May 2016 in our hospital were collected, and the MRI image features of osteonecrosis of the femoral head were summarized, compare the positive rate, sensitivity and specificity of CT and MRI in diagnosing femoral head necrosis and analyze the accurate diagnosis rate of femoral head necrosis at different stages by CT and MRI. Results The positive rate, sensitivity and specificity of MRI in diagnosing femoral head necrosis were 92.06%, 90.47% and 84.12%, which were obviously higher than those of CT, 79.36%, 73.01% and 68.25%, the difference was statistically significant(P<0.05). MRI images show that stage I to stage II necrosis of the femoral head presents uneven bone marrow signal inhomogeneity in the diseased side of the femoral head, irregular flaky T1 signal was shown in the femoral head, and a small amount of long T1 signal is found in the joint cavity of a few patients, the coronal T1WI showed marked "line sign". Conclusion The positive rate, sensitivity and specificity of MRI scan in the diagnosis of adult femoral head necrosis are high, which can effectively improve the accuracy of early diagnosis, and is worthy of clinical promotion.