Objective: To evaluate the efficacy and safety of 585 nm Q-switched laser in the treatment of acne inflammatory lesions and postinflammatory erythema. Methods: A total of 25 patients with moderate facial acne, symmetrical distribution of inflammatory lesions and postinflammatory erythema on both sides of the face, were enrolled. Among the 25 patients, 22 patients completed all the treatment and evaluation, and 3 patients were lost to follow-up. 585 nm Q-switched laser was used on a randomly selected side of the face for three times of treatment at a 2 week interval. The evaluations were made before each treatment, 2 and 4 weeks after the last treatment, therefore the evaluation time points were before the treatment, weeks 2, 4, 6, and 8, respectively, for a total of 5 times. Acne severity was assessed using the investigator’s global assessment (IGA) score, and erythema severity was assessed using the investigator’s subjective erythema score and narrow-spectrum reflectance spectrophotometer at each follow-up. Results: After 3 times of treatment, there was statistically significant difference between the IGA score in week 8 and before treatment on both sides(Z=2.64, P<0.01; Z=2.67, P<0.01). There was no significant difference in IGA score between the treatment side and the control side before treatment and in week 8 (P=0.59, P=0.26). There was statistically significant difference between the investiga-tor’s subjective erythema score in week 8 and before treatment on the treatment side(Z=4.24, P<0.01), while no significant difference was showed on the control side(Z=1.73, P=0.08). In week 8, the investigator’s subjective erythema score of the treatment side was lower than that of the control side (Z=3.61, P<0.01). The erythema index of the treatment side was significantly decreased at 5 time points (P<0.01), and the index decreased significantly in week 8 compared with the index before treatment (P<0.01), while the erythema index of the control side was not significantly different at 5 time points. The treatment related adverse events included erythema and edema after treatment and pain during treatment, the severity was mild to moderate, which resolved spontaneously within 1 to 3 days. Nine patients were very satisfied with the treatment, 7 patients were satisfied, and 6 patients considered average. Conclusion: 585 nm Q-switched laser has some effect in the treatment of postinflammatory erythema, and it ensures good tolerance and safety. There was no statistically significant difference between the treatment side and the control side on the improvement of acne inflammatory lesions.