The mathematical physics essentiality of phenomenological similitude is pointed out to have the same dimensionless models , including the same model structures and the same values of all characteristic numbers in a dimensionless normalized coordinate basis 摘要指出了现象相似的数学物理本质是它们在同一个量纲为1的单元座标体系中有相同的量纲为1的模型:模型的结构相同且各特徵数数值一对应相等。