To relevantly diagnose the histological grade of malignancy before treatment, it is most important to select therapies of lower gingival squamous cell carcinoma. We examined the relationship among each factor of histological grade of malignancy, metastasis of lymph nodes, effectiveness of preoperative treatment, and prognosis of 29 cases of lower gingival squamous cell carcinoma. The histological grade of malignancy was classified according to seven factors, that is, differentiation, nuclear polymorphism, mitosis, mode of invasion, stage of invasion, cellular response, and vascular invasion. Metastasis of lymph nodes is associated with mode of invasion, stage of invasion, and vascular invasion. Effectiveness of preoperative treatment is only correlated with vascular invasion. Poor effectiveness of preoperative treatment induced recurrence and the tendency of metastasis. As a result, their 5-year crude suvival rates were lower. Therefore, in decision of therapeutic strategies for lower gingival squamous cell carcinoma, we should particularly consider mode of invasion, stage of invasion, and vascular invasion.