Abstract: Calreticulin（CRT） is a highly conserved Ca²⁺ binding protein in eukaryotes and plays an important role in viral replication. To study the Secrt gene of Spodoptera exigua and its role in cells infected by Spodoptera exigua multiple nucleopolyhedrovirus（SeMNPV）, the complete open reading frame of 1 200 bp of Secrt gene encoding 399 amino acids was obtained by seamless cloning with the cDNA of host Se301 cell as the template. The relative molecular weight of SeCRT protein was 45.86 kDa, bioinformatic analysis showed that it had a signal peptide, no transmembrane domain, 2 O-glycosylation sites, 28 phosphorylation sites, and the terminal of the C domain had an ER retention signal HDEL, which was a hydrophilic protein located in the endoplasmic reticulum. The phylogenetic tree was constructed by the maximum likelihood method. The clustering results showed that the SeCRT was clustered with CRT of other Lepidoptera insects, and the similarity with the CRT of Spodoptera litura was as high as 98.25%. Real-time fluorescent quantitative PCR（RT-qPCR） showed that Secrt gene mRNA level first decreased, then increased, and finally stabilized when SeMNPV infected Se301 cells, indicating that Secrt gene responded to virus infection. Subsequently knockdown of Secrt expre-ssion in cells by RNAi interference resulted in a 43.4% reduction in SeMNPV virus DNA replication, suggesting that Secrt affects viral DNA replication. These results lay a foundation for further elucidating the molecular mechanism of host gene Secrt in SeMNPV infection and the mechanism of virus-host interaction.