Abstract: By using selective cultural media,Enterobacter closcae was isolated from the soil around a pesticide factory.For evaluating factors affecting E.closcae's potential in degrading residual dimethoate,a L16(44×23)orthogonal test was used for the design of the experiment.The results showed that sucrose as the conformable carbon source,10 mmolL-1 Cu2+,100 mgL-1 dimethoate,30 ℃,initial pH 8.0,3 gL-1 yeast extract as the conformable nitrogen source,and 36 h cultivation to yield a degrading rate of 58.90%.Statistical analysis by using DPS Data Processing System revealed that the ion exerted the most significant impact on the degradation rate,followed by pH,culture time,dimethoate concentration,temperature and carbon source in that order.