Reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide produced in cell metabolism, result in the disruption of cellular function and structure. Catalase (CAT), an enzyme which exists in almost all organisms including plants, invertebrates and vertebrates, acts in scavenging ROS. In this study, a sequence fragment encoding a CAT‐like protein from wheat aphids ( Sitobion avenae) was cloned. Amino acid sequence alignment showed this CAT shared relatively high conservation with CAT sequences from other insects. We detected cat mRNA levels at nymphs of different stages and adults and results showed that cat expression in adults was significantly higher compared to juvenile stages. At the third instar stage, ingestion of dsCAT significantly knocked down CAT expression. Continuous feeding of dsCAT mixed in an artificial diet led to reduced survival rate and ecdysis index. This study indicates that cat, a potential target gene for management of insect pests, is important for maintaining the survival of S. avenae.