Abstract: In order to explore the molecular mechanism of helmet development in Daphnia galeata, this study investigated the expression of two genes related to helmet development (DgTrepsin and DgFerritin) and changes of helmet morphology in D. galeata under RNA interference. The results showed that at a 2% concentration of E. coli, compared with the EGFP group, the DgTrypsin-interference group exhibited significant reductions in helmet length, relative helmet length, and the ratio of helmet length to head width, accompanied by a 27.45% decrease in DgDrypsin expression. However, no significant morphological or gene expression changes were observed in the DgFerritin-interference group at this concentration. When the concentration concentration of E. coli was increased to 5%, both the DgTrypsin and DgFerritin groups showed significant decreases in all three helmet morphology metrics, along with respective gene expression reductions of 55.96% and 40.39%, respectively. These results indicate that higher levels of RNA interference have a stronger inhibitory effect on the morphological changes and expression levels of the target genes. The findings demonstrate that DgTrypsin and DgFerritin genes are involved in the development of D. galeata helmet providing a valuable reference for further exploration of molecular mechanisms underlying the morphogenesis in Daphnia.