For over several decades, 595-nm pulsed dye laser (PDL) has been used effectively, reducing erythema and improving the pliability and texture of burn scars. Children usually tolerate PDL treatment as it is non-invasive and causes only mild pain compared to other laser treatments. However, currently, there are limited data on scar management in children who underwent PDL treatment, especially for Fitzpatrick skin types III and IV. The objective of the study was to identify the optimal parameters for the PDL treatment that induce inhibitory effects on scar tissue in children with Fitzpatrick skin types III and IV. Besides, the study assessed the usefulness of high-frequency ultrasound (20 MHz) and laser Doppler flowmetry in assessing these lesions. A total of 165 (79 males and 86 females) children with hypertrophic scars treated by PDL were assessed by the Vancouver scar scale (VSS), high-frequency ultrasound (20 MHz), and laser Doppler flowmetry. The parameters used for the 595-nm PDL treatment were pulse duration of 0.45 ms, fluence between 5 and 9 J/cm2, a spot size of 7 mm, and treatment intervals from 3 to 8 weeks. There were no significant differences between pretreatment and post-treatment in terms of the distribution of sex, type of skin color, and low and high fluences. While the mean scores of all scar parameters based on VSS, except thickness and pliability between pre and post-treatment, showed significant differences in ≤3-year-old children vs. to >3-year-old children, except for the subscore, a significant improvement was observed when PDL was initiated within 4 to 6 months of the scar age. In Chinese children with Fitzpatrick skin types III and IV, early intervention, appropriate treatment intervals, and low fluence of PDL were optimal parameters in treating hypertrophic burn scars. The combined high-frequency ultrasound and laser Doppler flowmetry assessment of scars helped assess these lesions and compare the efficacy of different treatment modalities.