Abstract: On the basis of analysis and synthesis of the substance and contents of map,by using comparative method,this paper proposes that POINT is the"cells"which construct map.From this proposal a general set expression of point is established.It points out that the expression is the function of the six variants,i.e.,the positioning basic information together with the information of property indicating the category,colour and intensity of colour.then,the expression of map element and finally,the general expression of map are deduced.As examples,expressions of points of different categories,different kinds of map elements and of several maps are deduced therefrom.The authors believe that by using these expressions further investigation can be made into the function and result of map as a means of information communication in the human cognitive process.