Femoral head necrosis is a common disease of the hip joint, and its incidence has been increasing in recent years. Its main harm is the pain and dysfunction of the diseased hip joint, which can affect the work and quality of life of serious patients. Early ischemic necrosis of the femoral head can be treated conservatively by decompression of the bone marrow cavity to control the progression of the lesion and maintain the function of the hip joint, while patients in advanced stages can only recover the function through artificial hip replacement, so early diagnosis of ischemic necrosis of the femoral head is very important to guide clinical treatment. Studies have shown that the onset of ischemic necrosis of the femoral head is associated with trauma, femoral neck fracture, long term use of hormonal drugs, hematologic disorders, non-specific joint inflammation, and a history of heavy alcohol consumption, with some patients having no clear causative factors. Various causes of femoral head ischemia lead to non-infectious inflammation of the hip joint, necrosis of bone tissue, incomplete repair, morphological and structural changes of the femoral head, and eventually cause joint dysfunction, which can develop unilaterally or bilaterally, with bilateral onset common in non-traumatic cases. The clinical manifestations are pain in the hip and groin area, which can be relieved by rest in the early stage, followed by joint movement and walking dysfunction, which can seriously affect the function of the hip joint in the late stage. Clinical classification of femoral head ischemic necrosis into stage IV: stage I: ischemic cell death stage; stage II: early stage of decomposition and repair; stage III: repair stage; stage IV: femoral head collapse and degenerative osteoarthrosis. Imaging classifies stages I and II as early, stage III as middle and stage IV as late according to clinical and pathological changes. The common methods of imaging diagnosis of ischemic necrosis of the femoral head include hip X-ray (DR, CR), CT and MRI examinations. X-ray (DR, CR) hip radiography is the most commonly used examination method, which has the characteristics of wide application of equipment, quick examination and relatively low cost, and can show clearly the deformation, collapse and marginal osteophytes of the femoral head in the middle and late stages, but it often cannot detect abnormalities in the early stage of femoral head necrosis. CT has high spatial resolution and density resolution, and is more sensitive to bone destruction and hyperplasia, and has obvious advantages over X-ray (DR, CR), which can clearly show the location and extent of lesions, femoral head deformation and marginal collapse, and has a greater guiding effect on clinical treatment, but for early ischemic necrosis of the femoral head, especially stage I or stage I-II femoral head changes, because of the lack of MRI is very sensitive to bone marrow signal and soft tissue changes, and has high resolution of soft tissue structures, so it can detect bone marrow signal changes, joint effusion, joint capsule and soft tissue signal changes at an early stage, so it has the advantage of sensitivity and high specificity for early ischemic necrosis of the femoral head, and early ischemia of the femoral head causes bone marrow fat cell necrosis of the femoral head and In addition, MRI can show the typical “double line sign” of high signal within the line like low signal ring at the edge of the weight-bearing area, and MRI can also clearly show the necrotic tissue breaking into the joint capsule, acetabular bone involvement, the nature of fluid accumulation in the joint capsule and joint MRI can be used to detect advanced femoral head deformation and collapse. In conclusion, MRI can be the first choice for early diagnosis of ischemic necrosis of the femoral head. For patients with clinical manifestations of ischemic necrosis of the femoral head, but no obvious lesions are found by X-ray or CT examination, MRI imaging of the hip joint should be chosen as early as possible for clear diagnosis.