Myzus persicae (Sulzer), which is also called the green peach aphid, is one of the most important pests in China. It has a wide host range and its adaptation to plants differs depending on the host. The host biotypes of M. persicae have not been identified; this provides opportunities to study the host specificity of this aphid. Further research may contribute to our understanding of species diversity, which demonstrates the value of investigating the host biotype of the green peach aphid. In this study, aphids were collected from peach, tobacco, and cabbage in the dry area of the Loess Plateau, China. The preference of M. persicae for different host plants and their morphological differentiation were studied by leaf selection and traditional morphometric analysis. The results of the tropism of M. persicae toward hosts showed that the preference for the three plant hosts of aphids originally from cabbage and tobacco was not apparent in the former experiment, but it became clearer in the latter . Throughout the trial period, aphids originally feeding on peach leaves did not show a preference for any of the three plant species studied. In the presence of the three plant hosts, 63.5%, 13.8%, and 8.2% of aphids feeding on tobacco chose tobacco, cabbage, and peach leaves, respectively. This indicates that this type of aphid prefers tobacco. The aphids originally on cabbage or peach leaves had no obvious preference for their original host plants. The preference of aphids originally feeding on cabbage for the three plant hosts was cabbage leaves > tobacco leaves > peach leaves. Regarding host selection behavior of aphids from peach leaves, they were in greater abundance than those on tobacco and cabbage leaves during the first 4 hours after feeding. However, after 4 hours, a comparison of the three plants indicated the largest number of aphids was on tobacco leaves while cabbage leaves contained the fewest aphids. Morphological variation in eight M. persicae feeding characteristics on the three host plants was examined by morphological analysis. These characteristics were an important feature used to differentiate the aphids. A comparison of these aphid characteristics on the three hosts revealed they were similar, but there were exceptions. The ratio of the length of the tarsus and the ultimate rostral segment of the aphids originating from the three hosts was not significantly different (P>0.05). However, there was a significant difference (P<0.05) in body length, the length of the tentacle details and the metapodium femur, and the ratio of antenna length to body length. Based on these characteristics, which of the three host plants the aphids originated from could be determined. Additionally, body width and the length of the siphunculus of aphids feeding on tobacco and cabbage were significantly greater than those of aphids from peach (P<0.05). The caudas of aphids on cabbage were significantly larger than those of aphids from the other two hosts (P<0.05). The ratio of the length of the cornicles and caudas from aphids originally on tobacco was greater than that for aphids on cabbage; compared with the aphids on peach, there was no significant difference (P>0.05). In terms of the antenna, which is used more for feeling, the aphids on cabbage had the longest ones. Regarding each antenna section, there were differences in the length of antenna segments III, IV, and V, and the base of the tentacles. The exception was the length of antenna segments I and II, where there was no difference among the aphids. These results indicate that the morphological characteristics of the aphids on the three plant hosts may change based on the host characteristics. A comprehensive analysis showed that aphids originally from tobacco may have a specific host biotype.