Triclosan (TCS) poses an ecological health risk due to its lipophilic nature, long half-life, and bioconcentration. To evaluate the toxicity of TCS on aquatic organisms, the life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to TCS were investigated. In this study, the fecundity of rotifers was promoted by 25 μg/L of TCS and inhibited by higher concentrations (100 μg/L, 200 μg/L). The reproductive period of rotifers was shortened by 46.24 % but the post-reproductive period was prolonged by 176.47 % in 200 μg/L TCS. Both population growth and life table parameters indicated that a high concentration of TCS (200 μg/L) had negative impacts on population growth. Transcriptomic analysis showed that the effects of TCS on the life history parameters and population dynamics of rotifers were determined by regulating the expression of functional genes in cilium organization and cilium assembly and involved in pathways of focal adhesion.