Abstract: The existing regularity which has an important influence on the design of map symbols is studied in this paper.The convention and the equivalent principle of map symbols are put forward and explained.The author differentiates the substantial object from the map symbol,and points out that the former is transferred into the latter only when the map communiction,i.e.,the map symbol convention process,occurs.The conception of the value and the price of the map symbol is defined and elucidated.Based on the analysis of the connotation and the denotation of concept,the author explains the conception of the connotation map symbol and the denotation symbol,and analizes their "reverse-transferring" relationship.Finally,a new classification principle of map symbols is put forward by the author.