The nerve innervating the biceps is the musculocutaneous nerve. The musculocutaneous nerve comes from the C5-6 segment of the cervical aponeurosis. The musculocutaneous nerve emanates from the lateral fasciculus and then travels obliquely through the rostro-humeral muscle and down through the biceps and brachioradialis muscles to innervate the three muscles above. The main role of the biceps brachii is to cause elbow flexion, and the flexion action of the biceps elbow needs to be accomplished with the triceps brachii muscle in diastole, and the biceps brachii reflex is a key reflex that is often examined in the upper extremity, and it is a deep reflex. When checking the patient to take a sitting position or lying position, elbow flexion at right angles, the examiner sitting position with the left hand’s thumb or lying position to take the left hand’s middle finger, placed in the patient’s biceps tendon position, and then hold the percussion hammer percussion of the left hand’s thumb or middle finger, the reflex will be seen in the contraction of biceps muscle caused by the flexion of the elbow movement, the nerve injury movement will appear obstacles.