The small black spots left behind by acne are called post-inflammatory hyperpigmentation, which usually starts slowly and can be removed through temporary observation, drug intervention and physical therapy. 1. Temporary observation: the phenomenon of post-inflammatory hyperpigmentation is more common in the clinical aspect, and some patients will fade away with the passage of time, which will not affect the health and does not need special treatment, and can be temporarily observed. But need to pay attention to daily sunscreen. 2. Pharmacological intervention: patients can use retinoic acid cream, Apadalin and other drugs to promote skin epidermal renewal, reduce the phenomenon of subcutaneous melanin deposition. 3. Physical therapy: For the symptoms of inflammatory hyperpigmentation left by acne, laser treatment can be used to carry out selective photothermal effect on the precipitated melanin, so as to achieve the purpose of lightening hyperpigmentation. It is recommended that patients with black spots left behind by acne can cooperate with doctors for standardized treatment to improve the local appearance.