Vague needle-like pain in the left arm is commonly caused by trauma to the left arm and cervical spondylosis, as follows: First, trauma to the left arm: such as muscle and tendon injury or fracture, can be manifested as vague needle-like pain symptoms during the recovery period of the injury, mainly caused by surrounding inflammation and edema. Second, cervical spondylosis: In the early and middle stages of cervical spondylosis, due to inflammation and edema of the nerve roots, the patient will have radioactive needle-like pain in the left arm, and the pain symptoms occur intermittently and can be gradually relieved, and the patient will not have any pain symptoms when he/she gets better. After a detailed physical examination and ancillary tests, the cause of the vague needle-like pain in the left arm can be diagnosed. If the cause is determined, treatment should be actively carried out, which can make the above clinical symptoms be relieved or even disappear completely and will not affect the patient’s normal life and work.