A method of tire specification extraction was presented. First, in image pre-processing, iterative least square method was used to fit accurate positioning of the circle center, and coordinate transformation and bilinear interpolation stretching were used to preprocess tire image. Then, window transform was used to reduce image dimensions from two-dimensional to one-dimensional vector, and thus one-dimensional vector was proposed to construct the sawtooth with extreme points. Finally, by using the parameters, the characteristics of the waveform were described to extract character region of tire specifications. Experimental results show that this method can effectively extract the tire specification.