Actions and interactions of heavy metals (cadmium, zinc and plumbum) and polycyclic aromatic hydrocarbons (PAHs) [phenanthrene, fluoranthene, benzo(a)pyrene] on the soil urease and dehydrogenase activity were studied after 49 days exposure. The experimental approach was based on the uniform design which can cut the experiment time and improve the efficiency of experiments. Data treatment was essentially based on the multiple regression technique. The results showed that the action and interaction between heavy metals and PAHs were strongly dependent on the time of pollution. The dehydrogenase exhibits more sensitive to the combined pollution than urease. The negative interaction between Zn and Cd to hydrogenase activity and the combined stimulatory activity of Phenanthrene and Benzo(a)pyrene (or fluoranthene) to soil enzyme were observed. The interactions between Zn (Cd) and phenanthrene towards urease (dehydrogenase) were positive, and the interaction between Zn and benzo(a)pyrene to urease activity was negative. This study corresponds to exploratory phase in order to reveal interaction effects of heavy metals and PAHs on the soil enzyme and then to set up more in-depth analysis to increase progressively the understanding of the ecotoxicological mechanisms involved.