The detection of traffic sign is the crucial technology of traffic sign recognition system. A method of traffic sign detection based on image color and shape is proposed. Firstly, the image is pre-processed by gray stretching and noise filtering, and then the color image is segmented by improved K-means clustering algorithm. Finally, the shape detection technology based on Hough transform is used to locate the special shape of traffic signs, so as to realize the detection of traffic signs. The experimental results show that the average accuracy of the detection results under various complex background conditions is 93.0%, which is better than other algorithms under the same conditions and has high real-time performance.