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<i>Trichogramma pretiosum</i> Riley is an important natural enemy and biological control agent of lepidopteran pests. <i>Wolbachia</i> is an intracellular endosymbiont that induces parthenogenesis in the parasitoid <i>T. pretiosum</i>. In this paper, the sublethal effects of the antibiotic tetracycline hydrochloride on the development and reproduction of <i>T. pretiosum</i> were studied. Emerged females were fed with sublethal concentrations (LC₅, LC₁₅, and LC₃₅) of tetracycline for ten generations. The biological parameters (longevity, parasitized eggs, and fecundity) of treated females significantly reduced compared with the control Moreover, the percentage of female offspring in the treatments significantly reduced, but the percentage of male offspring significantly increased. In addition, the <i>Wolbachia</i> titer sharply reduced after two generations of antibiotic treatments, but it could still be detected even after ten successive generations of antibiotic treatments, which indicated that <i>Wolbachia</i> was not completely removed by sublethal concentrations of tetracycline. The control lines with higher <i>Wolbachia</i> titers produced more female offspring than the tetracycline treatments with lower <i>Wolbachia</i> titers, indicating that the <i>Wolbachia</i> titer affected the sex determination of <i>T. pretiosum</i>. Our results show that sublethal concentrations of tetracycline had adverse effects on the development of <i>T. pretiosum</i>, and <i>Wolbachia</i> titers affected the sexual development of <i>T. pretiosum</i> eggs.