Objective To explore the effects of sequential application of intensive pulsed light and carbon dioxide laser in treating the hypertrophic scars of burn children at early stage. Methods A retrospective cohort before-after control study in the same patients was conducted. From January 2016 to December 2018, 145 burn children with hypertrophic scar at the early stage who met the inclusion criteria were admitted to the First Hospital of Jilin University, including 82 males and 63 females, aged 1 to 12 (3 (2, 6)) years. All the children were firstly treated with intense pulsed light therapy (no anesthesia or intravenous-inhalation combined anesthesia) at an interval of once per month, and then changed to carbon dioxide laser therapy (topical anesthesia or intravenous-inhalation combined anesthesia) when the degree of scar hyperemia was reduced, at an interval of once every 3 months, for a total of 3 times. Before the first intense pulsed light treatment (hereinafter referred to as before the first treatment) and 3 months after the last carbon dioxide laser treatment (hereinafter referred to as after the last treatment), scar scoring was evaluated by Vancouver Scar Scale (VSS), and scar hyperemia (denoted as hemoglobin level) was measured with Antera 3D^® camera. The times of intense pulsed light, the time of single treatment, the anesthesia method, and the time of intravenous-inhalation combined anesthesia of intense pulsed light and carbon dioxide laser treatment were analyzed. After the last treatment, Likert Scale was used to evaluate the efficacy satisfaction of both doctors and patients. Adverse reactions were recorded during the treatment. Data were statistically analyzed with Wilcoxon signed rank sum test, and paired sample

test. Results The color, vascular distribution, thickness, and softness scores, and total score in VSS scoring of scars of children after the last treatment were significantly lower than those before the first treatment (

=-6.05, -10.34, -9.84, -9.28, -10.43,

<0.01). The hemoglobin level of scar of children after the last treatment was 1.86±0.24, significantly lower than 2.27±0.32 before the first treatment (

=17.65,

<0.01). A total of 411 times of intense pulsed light therapy were performed, (2.8±0.6) times per person, and the single treatment time was 35 (20, 45) s. There were 392 times (95.38%) without anesthesia, and 19 times (4.62%) with intravenous-inhalation combined anesthesia with time of 6 (5, 8) min. The single treatment time of carbon dioxide laser therapy was 5 (3, 10) min. There were 364 times (83.68%) of topical anesthesia and 71 times (16.32%) of intravenous-inhalation combined anesthesia with time of 10 (8, 15) min. After the last treatment, the efficacy satisfaction scores of doctors and patients were (4.3±0.7) and (3.8±1.0) points, respectively. Blisters occurred in 5 cases after intense pulsed light treatment, which were healed naturally after drainage. One child developed local skin infection, skin redness and swelling accompanied by purulent exudate after carbon dioxide laser treatment, which was improved after skin disinfection and external use of mupirocin ointment. No inflammatory pigmentation, worsening of hyperplasia of scar, erythema, or other skin adverse reactions or anesthetics-related adverse reactions occurred in any child. Conclusions Sequential application of intense pulsed light and carbon dioxide laser to treat the hypertrophic scars of burn children at early stage can obviously improve the appearance and texture of scar, with higher satisfaction of doctors and patients and fewer adverse reactions.