Diagnostic methods of hip synovitis in children include detailed communication with the child (many times it is necessary to find out from the parents), physical examination, imaging tests, and diagnostic hip puncture. Children’s hip synovitis examination hip joint is in the state of internal rotation, walking limp, hip joint internal and external rotation and other activities are limited. Imaging examination, ultrasonography can find thickening or disorder of the synovial capsule structure of the hip joint, as well as unequal amounts of fluid around the hip joint. The anterior space of the femoral neck of the hip may be significantly widened. It is often dependent on the experience of the sonographer. An MRI can reveal the presence of early osteonecrosis of the femoral head, other joint disorders, and the amount of joint effusion. In addition to the above two methods, arthrocentesis can be performed to extract a clear yellowish fluid that can be negatively cultured with a bacterial smear. The above methods can confirm the cause of hip synovitis in children.