Effects of yeast extract, glucose, peptone, soil extract and metal ions Ca²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Al³⁺, Mn²⁺, Co²⁺, Zn²⁺, Li⁺, Cu⁺, Cu²⁺, Ba²⁺, Ni²⁺ on degradation of p-nitrophenol(PNP) by DLL-E4 (Pseudomonas putida) were studied. The results show that addition of a proper amount of yeast extract, glucose and peptone could promote the degradation of PNP by DLL-E4, but the addition of soil extract could not. All the metal ions, except Li⁺ and 0.1mmol Fe³⁺ could affect removal of PNP by this strain. The effects of Ca²⁺, Mg²⁺ and Mn²⁺ were low, the effects of Fe³⁺, Fe²⁺, Al³⁺, Ba²⁺ and Zn²⁺ were high when in high concentration, whereas the effects of Co²⁺, Cu²⁺, Cu⁺ and Ni²⁺ were high, too, even in residual concentration.