Oral squamous cell carcinoma is a common malignancy in the head and neck region. Brachytherapy after radical surgery has achieved much progress as a cancer adjuvant treatment. This study focused on the pathologic characteristics of the patients with oral squamous cell carcinoma who underwent seed implantation after radical surgery, and the relationship of these characteristics with prognosis. Thus, 76 patients with oral squamous cell carcinoma, who were treated with surgery and subsequently with iodine 125 (125I) radioactive seed implantation, were recruited in this study. We summarized the demographic information, tumor size, location, clinical stage, prognosis, and pathologic characteristics, and discussed the correlations between prognosis and histologic features of oral squamous cell carcinoma after seed implantation. The data showed that the median age was 64 years old, the male/female ratio was 47/29, and the frequent location of the carcinoma was the tongue (35.5%). The median follow-up time was 126 months, and of the patients, 52 (68.4%) exhibited recurrent tumors. The 5-year survival rate was 81.5%, and the local control rate in 6 months was 95.3%. Microscopically, 25 cases demonstrated lymph node metastasis, there was obvious necrosis in 13 cases, and 55 cases exhibited confirmed adjacent tissue invasion including muscle, gland, vessel, nerve, and bone infiltration. Among those, vascular infiltration (13 cases) was significantly correlated with tumor recurrence (P < .05). This study suggests that detailed pathologic diagnosis and microscopic description, especially of vascular infiltration, was valuable in the prognosis prediction of brachytherapy.