Circular RNA (circRNA) plays a vital role in the occurrence and development of nasopharyngeal carcinoma (NPC). However, the role of certain specific circRNAs in NPC are still unknown. In this study, collect tumor samples and adjacent normal tissues from clinical NPC patients and detect the expression of circSOX9 by qRT-PCR. Use nucleoplasmic separation analysis, RNase R digestion assay and FISH to detect the characteristics of circSOX9. After knocking down circSOX9, clone formation experiment and transwell assay were used to detect the proliferation and invasion ability of nasopharyngeal carcinoma cells HONE1 and CNE2, and western blot was used to further detect the level of epithelial-mesenchymal transition (EMT). Use the database to screen for possible downstream target genes and verify them with dual-luciferase experiments. Bioinformatics analysis showed that circSOX9 was significantly up-regulated in NPC, and its expression level was positively correlated with the malignant progression of cancer. Data from function gain or loss studies showed that decrease of circSOX9 inhibited the invasion and proliferation of HONE1 and CNE2 cell lines. Further analysis proved that miR-485-3p was the downstream target of circSOX9. The luciferase test showed that by acting as a molecular sponge of miR-485-3p, circSOX9 promotes the proliferation and invasion of NPC cells, while miR-485-3p can target the expression of SOX9. In conclusion, circSOX9 acts as an oncogene in the progression of NPC through miR-485-3p/SOX9, indicating that circSOX9 can be used as a potential therapeutic target and predictive marker for nasopharyngeal carcinoma.