This paper studies the mountain place name characters of the "Shuo wen jie zi", including eleven ancient Chinese characters: "Nao(峱), Yi(嶧), Yu(嵎), Yi(嶷), Min( ), Ji( ), Jie(巀), Xue(嶭), Hua(華), Guo(崞), Yang(崵)". Those characters are all from the same radical of the "San"—mean about mountain on "Shuo wen jie zi", and neighbor in the "San" radical. Mountain place name characters in "Shuo wen jie zi", the character structure all added a radical "San", making it become a synthetic character. However, ancient Chinese geographical literature, the mountain place name not necessarily have the radical "San". Therefore, this paper will focus on the mountain place name characters of the "Shuo wen jie zi", research on structural principle related and the use cases on ancient literatures.