Polycyclic aromatic hydrocarbons (PAHs) are common persistent organic environmental pollutants, which enter the ecosystem through the food chain and directly endanger human health and the safety of the entire ecosystem. To investigate effects of low-molecular-weight organic acids on degradation of phenanthrene and bacterial community structure in soil, changes in soil phenanthrene content during 0-180 d after addition of different organic acids were assessed via variations in indoor culture characteristics of soil bacterial community types and quantities via high-throughput Illumina Miseq. Consequently, addition of low-molecular-weight organic acids significantly promoted phenanthrene degradation in soil, and the first-order reaction kinetids revealed that acetic acid had the most significant effect on phenanthrene degradation. Considering the bacterial community structure, addition of low-molecular-weight organic acids reduced the number of operational taxonomic units (OTUs) and the diversity of bacterial flora but increased the abundance of PAH-degrading bacteria. The total number of bacterial OTUs displayed a decreasing trend with time, and the number of unique species initially displayed an increasing trend, followed by a decreasing trend. Six typical phenanthrene-degrading bacteria were detected:Bacillus, Sphingomonas, Massilia, Azospirillum, Paraburkholderia, and Rhodococcus. These results provide a basis and a scientific reference for phytoremediation of PAHs contaminating soil.