<p>A combined chemical-biological treatment study of oily sludge was carried out using a chemical surfactant and <i>Pseudomonas stutzeri Lh-42</i> isolated from oilfield soil. As a result, most of the Total petroleum hydrocarbo in the sludge was eluted by the chemical surfactant and the residual oil that was difficult to elute was further removed by <i>Pseudomonas stutzeri Lh-42</i>. This method greatly improved the removal of Total petroleum hydrocarbo from the oily sludge. In this study, the oiled sludge samples were first fully characterised and the initial Total petroleum hydrocarbo content was 52,400 mg kg⁻¹, containing a large amount of organic matter such as polycyclic aromatic hydrocarbons. In the first step of the treatment study, the oiled sludge was treated with a screened chemical detergent and the resulting oiled sludge had a Total petroleum hydrocarbo content of 8900 mg kg⁻¹ with a removal rate of 83%. In the second step, the sludge was treated with <i>Pseudomonas stutzeri Lh-42</i> in three different conditions: free, immobilised and free plus immobilised. The removal rate of total petroleum hydrocarbo from the sludge was 92%. This combined chemical-biological treatment of oily sludge will provide a new strategy for the design of oily sludge treatment processes.</p>