Buzura suppressaria Guenee (Lepidoptera: Geometridae) is a defoliator that seriously harms eucalyptus trees in South China. Buzura suppressaria nuclear polyhedrosis virus (BsNPV) is a baculovirus that infects B. suppressaria with high specificity and efficiency. Transcriptomes of B. suppressaria were sequenced before and after BsNPV infection using an Illumina-based platform to probe for differentially expressed genes (DEGs) of B. suppressaria after viral infection. On average, ∼57.4 million high-quality clean reads were generated and assembled de novo into 69,761 unigenes. The NCBI nonredundant protein, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene ontology (GO), and Cluster of Orthologous Groups databases were used to annotate unigenes through NCBI BLAST; 33,575 unigenes (48.1%) were then mapped to at least one of these databases, and 4,366 unigenes (6.3%) were mapped to all databases. Differential expression analysis showed that 25,212 unigenes were upregulated and 22,880 unigenes were downregulated in at least one pairwise comparison. Control versus 48 h had more DEGs than other two pairwise comparisons in either the GO or KEGG database, because the number of regulated gene would increase as BsNPV infected more tissues and would decrease as more tissues were disabled. To ascertain B. suppressaria immune response to BsNPV infection, DEGs were annotated to the GO and KEGG databases. In total, 89 GO categories are related to immune response and 1,007 DEGs are annotated to these GO categories. Furthermore, 7 downregulated DEGs and 37 upregulated were obtained simultaneously in all three groups. These DEGs were considered to possess a central role throughout viral infection.