The clay with high oil content form soil lumps, which is hard for microbes to repair. In this paper, the bioaugmentation and biostimulation technology were applied to improve the bioremediation effect of the soil with high oil content, that modified by local cow dung and sandy soil, the ecological toxicity of the soil after restoration was further analyzed. After 53 days of bioremediation, the degradation efficiency with respect to the total petroleum hydrocarbons (TPH) content reached 76.9% ± 2.2%. The soil bacterial count of M5 group reached log10 CFU/g soil = 7.69 ± 0.03 and the results were better than other experimental groups. The relative abundances of petroleum-degrading bacteria added to M5 remained high (Achromobacter 9.44%, Pseudomonas 31.06%, and Acinetobacter 14.11%), and the proportions of some other indigenous bacteria (Alcanivorax and Paenibacillus) also increased. The toxicity of the bioremediated soil was reduced by seed germination and earthworm survival experiments.