Phytoremediation is the most eco-friendly, economically sustainable, cost-effective technology available for the biodegradation of soil pollutants, while crude-oil-contaminated soil is susceptible to many factors in the process of phytoremediation, including climatic conditions, landform and soil properties, etc. The main properties of the Loess Plateau are high degree of salinization, an arid, and lack of soil fertility, thereby there are obvious regional vegetation distribution in this area. Compositae have strong drought resistance and tolerance and it is a ubiquitous plant growing wild and widely distributed throughout Northwest China. However, the phytoremediation effect of crude oil contaminated soil by Compositae has not been further studied in the Loess Plateau. Thus, in order to analyze and compare the phytoremediation efficiency of Medicago sativa and Coreopsis lanceolata on oil-contaminated soil in eastern Gansu Province of the Loess Plateau. The indigenous plants M. sativa and C. lanceolata were selected as the test plants, and a five months site remediation experiment was conducted in Changqing Oilfield Company, Qingyang City of Gansu Province. The changes of TPH (Total petroleum hydrocarbon, TPH) removal rate, plant growth index, soil physical-chemical properties and enzyme activities as well as microbial community structure in root-zone soil of M. sativa and C. lanceolata under different crude oil concentrations, i.e., light pollution group (TPH=3%), moderate pollution group (TPH=7%) and heavy pollution group (TPH=9%), were measured. We found that: (1) With the crude oil concentration increase from 3% to 9%, the removal rates of TPH in the root-zone soil of M. sativa were 69.88±4.16%、42.59±3.94%、19.20±2.77% and 2.01±0.19%, while were75.33±2.91%、74.87±2.79%、42.47±1.99% and 2.20±0.51% in the root-zone soil of C. lanceolata, respectively. (2) The emergence rate and chlorophyll a/b value of the two tested plants were not significantly affected by crude oil concentrations at 3%, while the effects of oil concentrations ranged from 7% to 9% on seedling emergence rate, chlorophyll a/b value, aboveground and underground dry weight, root vitality and root-shoot ratio of M. sativa were relatively significant (P<0.05). (3) Oil concentration ranged from 3% to 7% had relatively little inhibition on soil available P content in the root-zone soil of M. sativa (P<0.05), while the soil pH, urease and alkaline phosphatase activities in the root zone of C. lanceolata were significantly higher than those of M. sativa in the concentration ranged from 7% to 9% (P<0.05). (4) High throughput sequencing results showed that the relative abundance of crude oil degrading bacteria, i.e., Alcanivorax, Marinobacter, Halanaerobium, Halomonas and Nocardioides, etc. in the root-zone soil of C. lanceolata were significantly higher than those in the M. sativa (P<0.05). (5) Variance decomposition results indicated that the inhibition of oil concentration on the physiological characteristics of M. sativa was the decisive factor limiting the root zone soil TPH removal rate, while the combined effect of soil physicochemical × microbial characteristics was the main environmental factor determining the root zone soil TPH removal rate of C. lanceolata higher than that in the treatment group of M. sativa (P<0.05). In conclusion, the phytoremediation efficiency of C. lanceolata on crude-oil-contaminated soil in eastern Gansu Province of the Loess Plateau is better than that of M. sativa.