This paper mainly discusses how to realize the symbolization control of digital maps through symbolization control knowledge. First, the author briefly introduces basic concepts and means of realizing symbolization control of digital maps after analyzing the current problems of digital map symbolization. Then the author analyzes the composition of the symbolization control knowledge, and proposes some important concepts such as the expression of geographic attributes, the annotation's positional control code and the format string expression. Finally, the author designs and realizes the symbolization control interface with man-machine interaction. Practice has also proved that it is effective to realize the symbolization control of digital maps through knowledge of symbolization control.