Extracellular enzymes produced by thermophilic bacteria played an important role in promoting the reduction of penicillin fermentation residue after appropriate amounts of metal ions are added in this study. The results showed that soluble chemical oxigen demand (SCOD) quickly reached the maximum value of 3943 mg.L-1 within 2 h during biological pretreatment by thermophilic bacteria at an optimum value of 200 mu mol.L-1 Na+ with a suspended solid (SS) removal rate of 90.96%. Na+ also promoted NH4+-N. At 200 mu mol.L-1 K+ and at 20 h, SCOD increased, and its maximum concentrations were higher than those of the blank test. NH4+-N concentration also reached 102.04 mg.L-1. At 200 mu mol.L-1 Ca2+, the SS removal rate was 78.66%. Ca2+ addition did not promote the release of SCOD. NH4+-N was also inhibited.