To clarify the biological characteristics and metabolic pathways of Coccinella septempunctata feeding on artificial diets and Aphis craccivora, high-throughput sequencing technology was used to analyze relative transcription levels of C. septempunctata in 4^th instar larvae and adults. A total of 1234640650 clean reads had been screened out from 18 samples and 813335465 sequences have been compared the same with reference genome. DESeq2 analysis indicated that the expression levels of 11120 differentially expressed genes (DEGs) were significantly changed, and a total of 2280 DEGs were annotated in the KEGG pathway. Among C. septempunctata feeding on artificial diets, Cytochrome P450, Juvenile hormone epoxide hydrolase (JHEH), Juvenile hormone esterase (JHE), Juvenile hormone Ⅲ synthase (JHAMT), Dopa decarboxylase (DDC), Chitinase and most DEGs were down-regulated in 4^th instar larvae and male and female adults. DEGs of semen protein gene, 2-oxoglutarate dehydrogenase (sucA) and Insulin-like growth factor 2 upregulated in both male and female adults, and DEGs of lipoprotein upregulated in most females; Ecdysone-induced protein genes down-regulated in larvae. DEGs had enriched metabolic pathways related to 6 amino acids, 7 fat metabolisms, 2 starch and sugar metabolisms, and 7 vitamin-related metabolisms in KEGG. Among them, most genes of amino acid metabolism pathway of the C. septempunctata feeding on artificial diets down-regulated; whereas fat metabolism mostly down-regulated in adults and upregulated in larvae, starch and sugar metabolisms mostly upregulated in adults and mostly down-regulated in larvae, and vitamin mostly down-regulated in larvae. Quantitative real-time PCR verification showed that the sequence quality of transcriptome met the basic requirements for transcriptome data analysis. These transcriptome data provide reference for further optimization of artificial diet and promote the improvement of artificial diet formula.