Took phenanthrene and pyrene as representative of polycyclic aromatic hydrocarbons (PAHs). The experimental period was 70 days. Pot experiments were conducted to investigate the mechanisms of the removal and remediation efficiencies of PAHs under different planting models using two plant species, white clover (Trifolium repens) and alfalfa (Medicago sativa) in a greenhouse. Phytoremediation of PAHs in soils at initial contents ranging from 20.05 to 322.06 mg·kg-1 was investigated under different planting patterns, and enhancement mechanisms were analyzed. Results showed that, 1) In the experimental concentration range,the dissipation rate of PAHs in soils growing multispecies was the highest, and was significantly higher than that of monoculture. At the 70d experiment, about 75.47%of Phe and 68.28%of Pyr was removed from the soils under mixed cropping;while only 31.79%and 64.03%of Phe and 27.97%and 52.18%of Pyr were removed under single white clover and alfalfa cropping, respectively. 2) Under the same treatment conditions, the concentrations of PAHs in root or shoot were lower in mixed cropping than that in monoculture, and in the shoot lower than in the root, and phenanthrene content was lower than that of pyr. And 3) the removal rates of phe which was removed by biological effect in clover, alfalfa and mixed groups were 26.69%, 58.98%and 69.84%respectively, the pyrene removal rates were 25.29%, 48.98%and 65.86%, significantly higher than that of non-biological effect. The plant-microbial interaction was the most important of all, the rates of phenanthrene and pyrene in clover, alfalfa group group and mixed group were 6.95%, 34.85%, 42.95% and 6.3%, 26.78%, 38.98%. Effect of microbial indifferent modes was the same. Effect of plants and plant-microbial interaction were higher in mixed mode than that of the single mode. Results from this study suggested a feasibility of the establishment of multispecies phytoremediation to improve the efficiency of bioaugmentation in decontaminating PAHs contaminated soils, decreasing crop accumulations to PAHs and reducing risks associated with PAHs.%以菲、芘为多环芳烃（PAHs）的代表，选择多环芳烃初始浓度在20.05~322.06 mg·kg-1的污染土壤为研究对象，采用温室盆栽的方法，选用三叶草（Trifolium repens）单种、紫花苜蓿（Medicago sativa）单种和三叶草-紫花苜蓿混种3种模式，通过测定实验70 d后土壤中PAHs的浓度，研究不同种植模式下植物对PAHs污染的去除效果和修复机制。结果表明，（1）在实验浓度范围内，在三叶草和紫花苜蓿混种模式下，土壤中PAHs的去除率最高，明显高于单种模式。在70 d的实验期间，约有75.47%的菲和68.28%的芘被降解，而单种模式下三叶草和紫花苜蓿对菲的降解率分别为31.79%和64.03%，对芘的降解率分别为27.97%和52.18%。（2）相同污染水平下，茎叶部PAHs的含量低于根部，菲的含量低于芘，混种模式下植物体内 PAHs 的含量低于单种模式下的含量。（3）生物作用对土壤中菲的去除率在三叶草、紫花苜蓿组和混合组中分别为26.69%、58.98%和69.84%，对芘的去除率分别为25.29%、48.98%和65.86%，明显高于非生物作用。在生物作用中植物-微生物的联合效应是最主要的，在三叶草组、紫花苜蓿组和混合组中对菲、芘的去除率分别为6.95%、34.85%、42.95%和6.3%、26.78%、38.98%。微生物作用在各种模式下相同，混种模式下，植物作用、植物-微生物联合效应均高于单种模式。说明借助多物种混合种植模式对改善PAHs污染土壤修复效果、减少植物体内PAHs积累和缓解生态风险具有可行性。
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