With the demanding of morphological features recognition in picking robot machine-vision system, preference artificial immune net (aiNet) was used as the image recognition algorithm, mainly modified the structure of the algorithm to promote the accuracy rate. The algorithm was modified according to picking environment and real-time require. The simulation proved the clustering accuracy of preference aiNet reached to 81.67% in the sunny day and 87.69% in the cloudy day. The modified algorithm has certain meaning in the next research of picking robot.