Abstract: Phenotypic plasticity is a given genotype which can produce different phenotypes in various environmental conditions. Due to traffic pollution from highways, the change of plant phenotypic plasticity comes as the response to the heterogeneous habitats. Plant phenotypic plasticity is an important ecological index to reflect the biological adaptive capacity of plants to different environmental conditions. Based on the survey of plant diversity in sample areas around the 309th national highway, the author not only measured several phenotypic plasticity indexes including the plant height, root length, leaf area and root-shoot ratio, but also investigated environmental parameters such as soil water content, traffic volume and the amount of dust absorption. The effects of traffic pollution on the plant phenotypic plasticity were analyzed in details. The results indicated that there were five kinds of plant in the sample areas including Artemisia capillaris Thunb., Chenopodium glaucum L., Artemisia argyi H. Lév. & Vaniot, Geranium carolinianum L., Rubus idaeus L., among which the dominant species were Artemisia capillaris Thunb., Chenopodium glaucum L. and Artemisia argyi H. Lév. & Vaniot. Through the traffic volume statistics, sample highway section was classified as twolane secondary roads. The distance from highway had a close relationship with the dust absorption amount of the leaves of Chenopodium glaucum L.. The correlation between the soil water content and the plant phenotypic plasticity index was that many phenotypic plasticity data, such as the plant root length, leaf area, root to shoot ratio and the plant multifarious index, increased with the decreasing of soil water content, while the plant height decreased. Several plants showed significant differences of phenotypic plasticity in different sample areas, such as plant height, root length, leaf area, root-shoot ratio and etc., indicating their unique suitability to heterogeneous habitats.