Abstract: Two isolates,sw03032 (Paecilomyces farinosus) and sw03085(P. fumosoroseus),were cultured in SDB media.The metabolites were extracted to study the pesticidal activities and impacts on acetyicholinesterase and carboxylesterase.The results indicated the two isolates could produce active compounds to poison tobacco aphides and reduce activities of the two important enzymes.Compared with CK2,in 12h,activities of acetyicholinesterase and carboxylesterase treated with different concentration crude toxins from sw03085 could reduce to 70.4%-29.8% and 79.5%-44.4% respectively.Treated with different concentration crude toxins from sw03032,activities of acetyicholinesterase and carboxylesterase could reduce to 38%-18.6% and 51.6%-59.5% respectively.Poisonous roles of the toxins from sw03085(P. fumosoroseus) to tobacco aphides were evidently higher than the toxins from sw03032 (P. farinosou).