Objective To explore the effect of micro-thinned anterolateral thigh flap and forearm flap on the repair of defects after oral cancer surgery. Methods From March 2020 to March 2023, 76 patients with oral cancer who underwent postoperative defect repair in Hunan Provincial People's Hospital were selected as the research objects. According to the random number table method, they were divided into reference group and observation group, with 38 patients in each group. The reference group was treated with forearm flap repair, and the observation group was treated with micro-thinned anterolateral thigh flap repair. The postoperative functional recovery, postoperative sensation, postoperative satisfaction, postoperative adverse reactions and complications, and postoperative donor site recovery were compared between the two groups. Results The flap survival rate of the observation group was 100.00%, which was higher than 97.37% of the reference group, but the difference was not statistically significant (P >0.05). The scores of appearance repair, mouth opening, closure, eating, language function, swallowing function, occlusion function and chewing function in the observation group were higher than those in the reference group, and the differences were statistically significant (P <0.05). The excellent and good rate of postoperative sensation in the observation group was higher than that in the reference group, and the difference was statistically significant (P <0.05). The scores of language, scar, sensation and eating satisfaction in the observation group were higher than those in the reference group, and the differences were statistically significant (P <0.05). The incidence of scar, pigmentation and paresthesia in the observation group was lower than that in the reference group, and the difference was statistically significant (P <0.05). There was no significant difference in the incidence of slow response, atrophy and ulceration between the two groups (P >0.05). There was no significant difference in the recovery of donor site between the two groups (P >0.05). Conclusion Compared with the forearm flap, the micro-thinned anterolateral thigh flap can effectively restore the appearance and function of the defect site after oral cancer surgery, and the donor site is less damaged. Meanwhile, the patient's aesthetic satisfaction is high, the incidence of adverse reactions and complications is low, and the application value is high.