Porcine pancreatic lipase was covalently immobilized on polyvinyl alcohol using adipoyl dichloride as a cross-linker. The effect of pre-treatment of lipase previously with various types of oils on immobilization efficiency was investigated. The increment in immobilization efficiency was observed after pre-treatment of lipases with oils. The highest immobilization efficiency obtained was 20% (v/v) for olive oil pre-treated lipase, which was 8 times higher than that of non-pretreated immobilized lipase. Immobilized lipase had better stability and had some advantages in comparison with free enzyme.