Developmental dysplasia of the hip is one of the common osteoarticular deformities, which refers to the abnormal correspondence between the femoral head and the acetabulum. It includes structural morphological abnormalities of bony, cartilaginous rows and soft tissues. The current concept of treatment for DDH is early diagnosis and early treatment. Ultrasonography is the main tool for early diagnosis of DDH, especially for infants under 6 months of age, and Graf is the most widely used ultrasonographic method to examine the hip joint. How should we interpret a Graf method static ultrasound report? Ultrasound is used to determine the final hip ultrasound staging by measuring the alpha and beta angles. What are the alpha and beta angles? The alpha angle is the bony apex angle, which reflects the bony socket apex; the beta angle is the cartilage apex angle, which reflects the cartilage socket apex. Type I (Ⅰa, Ⅰb) type is α angle ≥ 60b; Type II (Ⅱa+, Ⅱa-, Ⅱb, Ⅱc) is 43b ≤ α angle ≤ 59b (Ⅱa, Ⅱb type α angle = 50b to 59b; Ⅱc type α angle = 43b to 49b); Type D is 43b ≤ α angle ≤ 49b; Type III Ⅳ is α angle < 43< span="">b β angle determines the subtype of ultrasonic typing. Type I is a normal mature joint; IIa+ is a physiological immaturity; IIa- and above is a developmental defect; D type III type IV is a dislocated joint. All subtypes IIa- and above require treatment, and the earlier the treatment, the better the chance of obtaining a normal mature joint.