【Objective】 To screen reliable internal reference genes of castor，Ricinus communis，treated by glucose-fipronil (GTF) and the solvent dimethyl sulfoxide (DMSO)，and to provide a basis for studying the uptake mechanism of GTF. 【Method】Actin, ARC, ef1a, SamDC and TUA6 genes were selected as candidate reference genes. Specific primers for each gene were designed and real-time quantitative PCR was conducted. Five softwares，including geNorm, NormFinder, BestKeeper, Delta CT and RefFinder，were employed to analyze the gene expression stabilities in cotyledon of castor seedlings treated by GTF and DMSO with different concentration and time. 【Result】 The stabilities were variant according to different softwares. The rank orders of stability were geNorm: Actin= ef1a>SamDC>ARC>TUA6；NormFinder：SamDC>ARC>Actin>ef1a>TUA6; BestKeeper: Actin>ef1a>SamDC>ARC>TUA6；Delta CT: Actin >ef1a>SamDC>ARC>TUA6;RefFinder: Actin >SamDC>ef1a>ARC>TUA6. With a single analysis of DMSO treatment by RefFinder showed that ef1a>SamDC>Actin>TUA6>ARC.【Conclusion】Actin is the stablest reference gene under GTF and DMSO treatments, while ef1a is the stablest one under DMSO treatment.