Sympathetic denervation is associated with many diseases. Most cutaneous external monitoring indicators are non-invasive and used widely in clinical medicine. The external monitoring indicators of sympathetic denervation are reviewed to facilitate the clinical diagnosis of sympathetic diseases and the results of sympathectomy. Useful indicators of sympathetic denervation include sweating, warm skin, increased blood flow, Electrodermal Activity (EDA), pain response, skin integrity, and skin wrinkling. Sympathetic denervation can be assessed simply and accurately using many external indicators to diagnose sympathetic-related diseases or evaluate the effectiveness, complications, and prognosis of sympathectomy.