Previous studies have shown that Regiella insecticola modulated the parasitism rate in wheat aphid, Sitobion miscanthi. However, little is known about influences of the symbiont on wheat aphids by predators, the other important strategy used in biological control. Herein, we in the study examined effects of the R. insecticola on aphid population dynamics under non-consumptive effects, and predation of S. miscanthi under consumptive effects of the ladybeetle Harmonia axyridis, a major predator in field populations. The results showed that i) without exposure to the predator, R. insecticola led to an increase in aphid populations (e.g., higher intrinsic rate of increase); ii) compared to without exposure to the predator, the short-term exposure (i.e., 4 h) increased aphid populations (either symbiont infection or not), whereas a contrary result was observed under the relatively long-term exposure (i.e., 24 h); iii) compared to symbiont-free aphids, symbiotic aphids did improve defenses against H. axyridis in the consumptive assay, and mainly attributing to the increase of handling time (T-h) of the predator to symbiotic aphids. The study provides new insights on the roles of symbionts on biological control by predators and insect population dynamics.