下颌磨牙发育沟有着各种形态，作者采用国际通用的分类方法，将下颌磨牙发有沟的类型分为“Y5”、“Y4、“＋5”、“＋4”、“X5”、“X4”六种形态，经过计算机统计分析，得出结果；（1）下颌第一磨牙“Y5”的发生率最高，“X4”的发生率最低；（2）下颌第二磨牙“＋4”的发生串最高，“Y5”的发生率最低；（3）男、女间发生率经t检验无明显差异。本结果与人类下颌磨牙进化方向一致，对于指导临床治疗、人类学的研究均有非常重要的实际意义。 There are various forms of the development of mandibular molars, the authors use the internationally accepted classification method, the type of mandibular molars are divided into “Y5”, “Y4,” “+5”, “+4”, “X5”, “X4” (1) The incidence of “Y5” in mandibular first molar was the highest, and that of “X4” was the lowest; (2) The incidence of “+4” in mandibular second molar was the highest, The incidence of “Y5” was the lowest; (3) The incidence of male and female had no significant difference by t-test.This result is consistent with the evolutionary direction of human mandibular molar, which has very important practical significance for guiding clinical treatment and anthropology research .