Abstract: In the process of symbolization of electronic map, visual variable is the key. Through the analysis of shortages of visual variables and symbol constitution elements in the process of symbolization in the situation of electronic map, concept of constitution variables is brought forward. Then, profound meanings and representation forms of constitution variables are studied, and multifold symbol generation modes are discussed based on constitution variables. At last, electronic map symbol fast generation module is made to validate the theories, which proves that it is easier to draw symbols with computer and the symbols are preciser and prettier. On one hand, study of constitution variables and generation modes can make us understand visual variables deeply and boost the development of electronic map theories. On the other hand, it will also provide new method to the development of electronic mapping technologies and promote the evolution of automatization symbolization, individuation mapping, automatization mapping and intellectualized mapping.