To investigate the efficacy of isotretinoin combined with fire needle in the treatment of nodular cystic acne, and to analyze the imaging characteristics of laser confocal scanning microscopy and skin ultrasound before and after fire needle treatment. Methods A total of 87 patients with nodular cyst type acne admitted to our hospital from January to June 2023 were selected as the research objects. They were divided into control group (47 patients) and observation group (40 patients) by random number table method. The control group was treated with oral isotretinoin, and the observation group was treated with isotretinoin combined with fire needle. The clinical efficacy of the two groups was compared, and the microscopic changes before and after treatment were observed by skin laser confocal scanning microscope and skin ultrasound. Results There was no significant difference in the total effective rate between the two groups at 2 and 4 weeks after treatment (P >0.05). The total effective rate of the observation group at 6 and 8 weeks after treatment was higher than that of the control group, and the difference was statistically significant (P <0.05). Under the skin laser confocal scanning microscope, the acne showed that the hair follicles lost their original structure, and there was a circular low-refractive embolism in the superficial layer of the dermis. The skin ultrasound showed that the nodular cystic lesions had subcutaneous mixed echo and other imaging features. After the fire needle treatment, the confocal laser scanning microscope showed that the epidermis had returned to normal structure, and some showed that there were more high-lighting substances on the edge of the dermal papilla. Nodular cysts under skin ultrasound showed obvious regression without leaving traces. Conclusion Isotretinoin combined with fire needle in the treatment of acne has faster onset and definite curative effect. Skin laser confocal scanning microscope and skin ultrasound can be used to judge the efficacy of fire needle in the treatment of acne.