Apolygus lucorum is the predominant pest of Bacillus thuringiensis (Bt) cotton in China. 20‐hydroxyecdysone (20E) plays a key role in the reproduction of this insect. To better understand the mechanism underlying 20E‐regulated reproduction, the nuclear hormone receptor E75 isoform‐A of Ap. lucorum (Al‐E75A) was cloned and its expression analysed. A 2241‐bp sequence of Al‐E75A cDNA encoded an open reading frame of a polypeptide with a predicted molecular mass of 69.04 kDa. Al‐E75A mRNA was detected in female adult stages of Ap. lucorum with peak expression in 7‐day‐old animals. Al‐E75A was also expressed in several tissues, particularly in the fat body and ovary. A 3.2 kb Al‐E75A mRNA was detected in all tissues by Northern blot. The fecundity and longevity were significantly decreased in female adults treated with Al‐E75A small interfering RNA. The rates of egg incubation rates were considerably lower in the RNA interference‐treated animals compared to the untreated controls. In order to investigate the molecular mechanism underlying the effects described above, vitellogenin (Al‐Vg) was selected for further investigation. The expression pattern of Al‐Vg was similar to that of Al‐E75A and was up‐regulated by 20E. After knockdown of Al‐E75A, the expression profile of Al‐Vg and the protein levels were down‐regulated. These findings suggest that Al‐E75A plays a crucial role in the regulation of Al‐Vg expression in Ap. lucorum.