Chitin synthase is an indispensable enzyme that is involved in the synthesis of chitin, a key component of the insect cuticle during insect development, which has long been considered a potential target for pest control. The German cockroach Blattella germanica is a notorious urban pest that has developed resistance to more than one class of insecticide. Therefore, there is an urgent need to explore novel green molecular approaches for sustainable insect pest control. In this study, two chitin synthase (CHS) genes (BgCHS1 and BgCHS2) were identified for the first time in B. germanica: Phylogenetic relationships, motif patterns, and conserved domain regions of all the predicted CHS genes were identified. Furthermore, the function characteristic of the two BgCHS genes was studied using a microinjection-based RNAi system. The results showed that silencing of BgCHS1 and BgCHS2 both resulted in high mortality. Knockdown of the BgCHS1 gene resulted in impaired molting and abnormal development, while knockdown of the BgCHS2 gene expression resulted in abnormal development. Additionally, a large-scale dsRNA production system via Escherichia coli was built and a nanoparticle-based (Star Polymers, SPc) oral delivery system of an SPc-wrapped two dsRNA of dsBgCHS1 and dsBgCHS2 was evaluated, which resulted in a high mortality and ultrastructural changes in the integument and midgut of cockroach nymphs, respectively. This study illustrates the functions of the two novel identified CHS genes in B. germanica, which can serve as potential gene targets for controlling one of the most serious urban health pests. [ABSTRACT FROM AUTHOR]