Polycyclic aromatic hydrocarbons (PAHs) accumulate excessively in soil environment recently, posing a significant threat to soil ecology and human health. The application of plant growth promoting rhizobacteria (PGPR) with PAHs degradable capacity in assissting with phytoremedeation of PAHs contaminated soil has not been reported yet. The purpose of this study was to verify the feasibility of a novel PGPR-assisted phytoremediation strategy for the remediation of PAHs contaminated soil. A phenanthrene (PHE) degradable strain Serratia sp. DLN5 with great plant growth-promoting (PGP) traits was selected by two steps of bacterial culture and plant verification. Through a 40-d pot experiment, the effects of DLN5 application on rape (Brassica napus L.) physiology and phytoremediation efficiency were determined. The results showed that DLN5 inoculation significantly promoted the growth of rape cultivated in PHE contaminated soil (200 mg kg−1 PHE), mainly reflecting by the increase of root length (22.2%), net photosynthetic rate (334.9%) and the decrease of malonaldehyde (MDA) content (79.0% in roots). The inoculation of PGPR could also modulate the activity of enzymes that related to nutrient cycling and pollutant degradation in soil. Besides, the analysis of high-throughput sequencing of rhizosphere soil samples revealed that DLN5 upregulated the abundance of some bacteria, which could contribute to the enhancement of PHE degradation process (e.g., Flavobacterium, Methylophilaceae and Burkholderiaceae). Through the regulation of plant growth and rhizosphere bacterial community by strain DLN5, the phytoremediation efficiency of PHE contaminated soils by rape inoculated with PGPR was elevated from 71.5% to 82.5%. In general, this study proposed an innovative PGPR-assisted phytoremediation strategy, while the mechanisms in this remediation process were also be proposed, which might not affect the economic value of industrial crop, providing a theoretical basis for the practical application of PAHs contaminated soil.