1. A symbol recognition method for increasing the symbol recognition speed by the processor, comprising: acquiring a plurality of symbol images; obtaining a pixel density value and an aspect ratio of the symbol image; obtaining a plurality of center-point values and a plurality of radius values of the symbol images through processing the pixel density values and the aspect ratios of the symbol images based on a partitional clustering algorithm; acquiring an under recognized image; obtaining a pixel density value and an aspect ratio of the under recognized image; and comparing a distance between a recognized point value determined by the pixel density value and the aspect ratio of the under recognized image and one of the center-point value with the radius value corresponding to the center-point value; wherein determining the under recognized image is a single symbol image when the distance is smaller than the radius value corresponding to the center-point value, and determining the under recognized image is a connected symbol image when the distance is larger than the radius value corresponding to the center-point value.