Microbial in situ remediation for petroleum- contaminated aquifers has been widely concerned in recent years. However, there are much ionic components in groundwater, effect of which on these inorganic ions for microbial degradation of organic pollutants is still unclear. A batch of experiment was conducted to investigate the effect of seven inorganic ions (NO3-, PO4 3-, SO4 2-, Cl-, Ca2+, Mg2+ and Fe3+） commonly found in the contaminated groundwater of Zibo Qilu Petrochemical on microbial growth and biodegradation of benzene. The population characteristics of benzenedegrading bacteria were further explored using high- throughput sequencing technology. The results show that seven ions exist in a suitable ion concentration for the growth of microorganisms below or above which the removal rate of benzene is significantly reduced. Among them, the optimum concentration of NO3-, SO4 2- and Fe3+ is 0. 4 mmol/L, the optimum concentrations of PO4 3-, Cl-, Ca2+ and Mg 2+ are 0. 2 mmol/L, 0. 1 mol/L, 2. 5 mmol/L and 2 mmol/L, respectively. From the perspective of microbial content and its range of variation, NO3- ions in groundwater have the most significant effects on microbial growth and benzene removal, while other ions have less effect. Microbial tolerance to Cl- is the highest. The highthroughput sequencing results show that the domesticated benzenedegrading bacteria mainly belong to the strains of Desulfovibrio sp, Desulfosporosinus sp, Acinetobacter sp and Pseudomonas sp. The results provide a scientific basis for in- situ bioremediation of groundwater contaminated by oil.