A kind of pyrazolyl acrylniitrile compounds represented by the structures of formula I or stereoisomers thereof are disclosed in the present invention. Where in: R1 is selected from the group of substituents consisting of H, C1-C4 alkoxy C1-C2 alkyl, C3-C5 alkenyloxy C1-C2 alkyl, C3-C5 alknyloxy C1-C2 alkyl, C1-C4 alkylthio C1-C2 alkyl, C1-C5 alkyl carbonyl, C3-C8 cycloalkyl carbonyl, C1-C5 alkoxy carbonyl or C1-C5 alkylthio carbonyl; R2 is Cl or methyl; R3 is H, methyl, CN, NO2 or halogen. Or its stereoisomers.The Formula I compounds have high insecticidal activities or acaricidal activities, so they can be used as insecticide or acaricide.