In order to effectively control petroleum hydrocarbon pollution by immobilisation technology, it is necessary to understanding the degradation pathways of petroleum hydrocarbon in immobilised petroleum-degradation bacteria system. However, the adsorption in degradation process is rarely studied. In this study, adsorption process of petroleum hydrocarbon was synergistically studied by means of the surface properties, adsorption thermodynamics and molecular simulation. The results indicate that the immobilised petroleum-degradation bacteria have many holes for the bacteria to adsorb. The diesel adsorption by immobilised petroleum-degradation bacteria is a spontaneous, entropy-increasing and endothermic process. Diesel is first adsorbed to the surface of immobilised petroleum-degradation bacteria through hydrogen bonding, and then is biodegraded. This study provided substantial knowledge of immobilised technology in controlling petroleum hydrocarbon pollution.