Abstract: In order to explore the possibility of application of cyclodextrins(CDs) in high-efficient pesticides utilization,environmental protection and other areas,the β- CD,HP- β- CD and Me- β- CD with chlorpyrifos inclusion complexes were prepared after filtration and drying according to phase transfer theory and coprecipitation.The inclusion intermedia and three kinds of liquid and solid inclusion complexes were qualitatively confirmed using UV spectrum,differential thermal analysis and infrared spectroscopy.The results showed that the molar ratio of chlorpyrifos to β- CD,HP- β- CD and Me- β- CD was all 1∶ 1 and the stability constants were K β- CD =33.33 L/mol,KHP- β- CD =343.8 L/mol and KMe- β- CD =461.63 L/mol.The spectral characteristics different from that of the chlorpyrifos indicated that chlorpyrifos were inclused in the cave of CDs and had formed stable complexes.The toxicity test showed that the LC50 value of the β- CD,HP- β- CD and Me- β- CD with chlorpyrifos inclusion complex against grubs in laboratory was 16.09,10.78 and 12.28 μ g/mL,respectively.The results indicated that β- CD,HP- β- CD and Me- β- CD could form a stable inclusion complex with chlorpyrifos,and insecticidal effects of these complex was good.