In order to recognize the operation mode of electronic scanning radar, analysis is made to the working process and mode transition of the electronic scanning radar.The common sequence of two intercepted signal state transition sequences is extracted dynamically by using the score matrix, and the main pattern of the electronic scanning radar is recognized.The experiments demonstrate that:1) The length of the intercepted sequence has little effect on the sequence similarity; and 2) The increasing of types of tracking mode and the decreasing of the rate of the tracking mode are beneficial to the extraction of radar pattern.