With the continuous expansion of petroleum exploitation, a large amount of petroleum hydrocarbons has leaked into the Earth’s soil, which seriously threatens ecological health. Hence, a series of experiments were conducted to evaluate the performance of natural attenuation (NA), rice husk (RH), and biochar derived from rice husk (RHBC) in enhancing the bioremediation of petroleum-contaminated soil. When the biodegradation time reached 100 d, the total petroleum hydrocarbons (TPHs) biodegradation amounts of NA, RH, and RHBC were 3688.2, 4557.9, and 5913.3 mg/kg, which was equal to the biodegradation efficiency of 32.8, 40.6, and 52.6%, respectively. Compared with NA and RH, the biodegradation efficiency of n-alkanes C₁₁–C₁₅ (C₁₁ represents n-alkanes with 11 carbons, namely n-Hendecane) C₁₆–C₂₉, and C₃₀–C₄₀ in RHBC increased to 69.7~82.5%, 42.4~81.5%, and 30.2~48.1%, equivalent to 12.2~34.5%, 6.9~31.2%, and 13.5~37.1% more than NA and RH, respectively. Moreover, the half-life of biodegradation in RHBC was shorted to 83.3 d, equal to 49.7 and 67.9% of NA and RH, respectively. Furthermore, the application of RHBC could improve the dehydrogenase activity in soil and promote the growth and reproduction of petroleum-degrading bacteria (PDB), which enhances the biodegradation of petroleum hydrocarbons. This study exhibited that biochar formed from biomass pyrolysis is a potential biostimulator in enhancing the remediation of petroleum-contaminated soil by indigenous bacteria.