Objective To observe the clinical effect of CO2 lattice laser combined with nano fat injection in the treatment of hypertrophic scar. Methods A total of 56 patients with hypertrophic scar admitted to our hospital from January to June 2022 were selected as the research objects. They were divided into control group and study group by random number table method, with 28 cases in each group. The control group was treated with CO2 lattice laser, and the study group was treated with nano-fat injection on the basis of the control group. The clinical efficacy, modified Vancouver scar scale (mVss) score, scar thickness and adverse reactions were compared between the two groups. Results The total effective rate of treatment in the study group was 92.86%, which was higher than 78.57% in the control group (P0.05). Conclusion CO2 lattice laser combined with nano fat injection in the treatment of hypertrophic scar can improve the clinical treatment effect, promote the improvement of scar state, and will not increase the incidence of adverse reactions, with good efficacy and safety.