Abstract: Pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: aphidiae), is an important agricultural pest for a wide range of leguminous crops with a very strong reproductive capacity. Pea aphid is a well-studied species in terms of color polymorphism, which occurs as two distinct (red and green) color morphs. It has been proposed that the occurrence of this color polymorphism was a response to environmental factors (in particular pesticides) which increase the adapting ability of A. pisum to changed environment. The resistance of pea becomes weak or disappeared as pea exposed to red color morphs, indicating biological type characters of A. pisums. To learn pesticides effects on different color morphs of A. pisum, the specific activities of acetylcholinesterase (AChE), glutathione S-transferase (GSTs) and mixed function oxidase (MFO) of red and green morphs of A. pisum treated with different sub-lethal concentrations of avermectin were studied in this paper. The results showed that the specific activities of AChE, GSTs and MFO of red and green morphs of A. pisum treated with different concentrations (LC₂₀, LC₁₀ and LC₅) of avermectin were higher than those of the control after 24 h. Also the specific activities of GSTs and MFO improved with increasing sub-lethal dosage. However, the specific activity of AChE of red and green morphs ofA. pisum reached maximum values of 13.93 nmol·min^-l·mg^-l(pro) and 53.93 nmol·min^-l·mg^-l(pro), respectively, under LC₁₀. The specific activity of AChE of green morph of A. pisum was higher than of red morph, and GSTs showed the reverse trend. However, no significant trends were noted in specific activity of MFO between red and green morphs of A. pisum treated with different concentrations. The specific activities of AChE, GSTs and MFO of red and green morphs of A. pisum treated with LC₂₀, LC₁₀ and LC₅ of avermectin decreased or increased with time. Specially, the specific activity of GSTs of green morph of A. pisum treated with different concentrations of avermectin reached the maximum values which were 49.84 nmol·min^-l·mg^-l(pro) for CK, 48.87 nmol·min^-l·mg^-l(pro) for LC₅, 42.74 nmol·min ^-l·mg ^-l(pro) for LC₁₀ and 45.35 nmol·min ^-l·mg ^-l(pro) for LC₂₀ at 0 h and were significantly higher than those of the rest of the other time scales. In summary, the change in specific activities of AChE, GSTs and MFO of red and green morphs of A. pisum had obvious links with treated concentrations and time.