Abstract: Biochar is effective in remediating soil contaminated with petroleum. However, there is a lack of understanding regarding its combined impact with wetland plants on the removal of petroleum hydrocarbons from coastal wetland soils. In this study, typical petroleum-contaminated soils (sandy and clayey soils) in the Liaohe River Estuary Wetland were used as the target, and the local dominant wetland plant, reed (Phragmites australis), was selected to evaluate the removal characteristics of petroleum hydrocarbons by rhizosphere and non-rhizosphere processes of the plant using a root box device. And at the same time set up three treatments of biochar additions of no (control), low (5 g/kg), and high (25 g/kg) to investigate the effects of reed and biochar on petroleum hydrocarbon (total petroleum hydrocarbons: TPH, medium carbon chain hydrocarbons: C10-C20 and high carbon chain hydrocarbons: C21-C35) concentrations in soil, and further analyzed the relationship between the changes of soil microbial and enzyme activities and the petroleum hydrocarbons content, to reveal the main controlling factors affecting the removal of petroleum hydrocarbons. The results showed that plant presence had no significant effect on TPH or its fractions in either soil type (p>0.05) , whereas biochar amendment significantly enhanced hydrocarbon removal (p<0.05), while no significant interaction between plant and biochar treatments was detected (p>0.05). High-rate biochar application outperformed the low rate: under high biochar addition, TPH concentrations in sandy and clayey soils decreased to 64.48% and 54.65% of control levels, respectively; the C10-C20 fraction decreased to 52.00% and 67.14% of control, and the C21-C35 fraction decreased to 72.72% and 45.94% of control. Further analysis showed that biochar significantly enhanced the Gram-positive bacteria, actinomycetes, fungi, bacteria, Gram-positive to Gram-negative bacteria ratio, fungi to bacteria ratio, and total microbial population in sandy soil. Random forest analysis further suggested that, in sandy soil, biochar promoted the removal of medium- and long-chain petroleum hydrocarbons mainly by enhancing microbial activity. In the clayey soil, although biochar addition significantly increased carbon-degrading enzyme activities, these enzyme activities were not significantly correlated with changes in TPH or its fractions. This study showed that biochar was more effective than plants in removing petroleum hydrocarbons, and the removal effect was affected by the amount of biochar added and the soil texture.