RNA interference (RNAi) that is triggered by small or short RNAs has shown enormous potential in the development of pest control strategies. Two microRNAs (miRNAs), Csu-novel-260 and Csu-miR-14, were used in insect-resistant genetically engineered (IRGE) rice lines to confer resistance toChilo suppressalis. However, a risk assessment of RNAi-based products is essential to determine the safety of a biopesticide or IRGE crop for commercialization. The non-target organismFolsomia candida, which plays an important ecological role as a soil decomposer in agricultural ecosystems, was used to assess the risk of miRNAs Csu-novel-260 and Csu-miR-14. In this study, a dietary miRNA toxicity assay system was established inF. candida. The expression levels of target genes, survival rate, fecundity and body size were investigated to evaluate the effects of the miRNAs onF. candidaunder the worst-case scenario. The results showed that the dietary miRNA toxicity assay system could be used for risk assessment of miRNA inF. candida. The target genes of miRNAs were influenced by miRNA at some time points. However, no significant differences were observed in the life-table parameters inF. candidafed with a diet containing miRNAs. The dietary effects of two miRNAs onF. candidaare neutral.