Fipronil is the first phenylpyrazole insecticide introduced for pest control. In order to further study fipronil derivatives of better bioactivity and systemic property derived from the pyrazole-5-amine by addition reaction/elimination/substitution reaction, ten modified compounds were prepared. Their insecticidal bioactivities against the 3(rd) instar larvae of Plutella xylostella were determined. The data suggested that bioactivities of most of the compounds are higher than that of fipronil, while some of them showed only modest activity as compared with fipronil.