The psoas major muscle acts as a cushion between the kidney and the spine, separating the ureter from the tip of the transverse process of the lumbar spine. The fascia enveloping the psoas major is the iliac fascia, which is part of the intra-abdominal fascia and is laterally fused to the anterior lumbodorsal fascia covering the anterior aspect of the psoas. The iliac fascia is attached medially to the lumbar vertebral body, the intervertebral disc and the upper part of the sacrum, thus forming the sheath of the psoas major muscle. The sheath of the psoas major is so solid that the pus from the thoracic and lumbar vertebral tuberculosis can flow down to the femur after entering the sheath. What should we do to prevent the disappearance of the shadow of the psoas major muscle? Strengthen exercise and improve physical quality. Such as doing some flexion, back extension, left and right lumbar side bending, gyration and sit-ups, so that the lumbar muscles are developed and strong, ligaments are strong, joints are flexible, reduce the chance of disease. Avoid long-term fixed in a movement and mandatory bending action, such as standing for a long time can squat a squat, squatting not only to relax the muscles of the waist and legs to rest, but also to reduce the consumption of physical energy. Pay attention to various postures in life, such as extracting heavy objects from the ground, you should bend your knees and squat to avoid bending over to increase the burden; take heavy objects, the body as close as possible to the object, and make it close to the abdomen, both legs slightly squat.