Increasing attention has been paid to the challenging issue of environmental pollution by antibiotics in recent years, and the structure and functioning of aquatic ecosystems could be disturbed by residues remaining in the environment. To date, however, few attempts have been made to investigate the effects of tetracycline hydrochloride on life history traits of rotifers under different food densities. In this study, the effects of tetracycline hydrochloride concentration on life table demography of Brachionus calyciflorus under different Scenedesmus obliquus densities were studied. The results showed that tetracycline hydrochloride concentration and food density had significant effects on life expectancy at hatching, net reproductive rate, generation time, intrinsic rate of population increase, average lifespan, and proportion of sexual offspring of B. calyciflorus. In addition, the interaction of tetracycline hydrochloride concentration and food density had a marked influence on five demographic parameters, except for the intrinsic rate of population increase, in rotifers. The peak of age-specific fecundity in B. calyciflorus increased to a maximum and then decreased with increasing concentration of tetracycline hydrochloride under each food density. The effects of tetracycline hydrochloride on the growth and reproduction of B. calyciflorus presented a pattern of hormesis. Mixis rate of offspring in rotifers increased at the high concentration of tetracycline hydrochloride under the three food densities, and there were significant dose-effect relationships between tetracycline hydrochloride concentration and the proportion of sexual offspring at the 1.0×10⁶ cells/mL food density. Levels of food density played an important role in the poisoning effects of tetracycline hydrochloride on B. calyciflorus.