The objective of this research is to explore whether LncRNA RP11 23J9.4 can be used as a targeted marker for the treatment of thyroid cancer (TC), downregulation of LncRNA RP11 23J9.4 and X-ray radiation have synergistic inhibitory effect on TC. The expression of LncRNA RP11 23J9.4 in papillary thyroid carcinoma (PTC) cell was downregulated by cell transfection, and its inhibitory effect on PTC cells was proved through proliferation, invasion experiment, apoptosis, and cell cycle analysis. The transfected cells were irradiated with 2 Gy X-ray. The above methods were also used to detect whether they had synergistic inhibitory effect on TC. The expression of Axin2 gene and protein were detected by real-time PCR, Western blotting, and immunohistochemistry. On the one hand, it is proved that downregulating the expression of LncRNA RP11 23J9.4 can inhibit the development of TC through Axin2. On the other hand, it is clear that downregulation of LncRNA RP11 23J9.4 and X-ray radiation have synergistic inhibitory effect on TC. LncRNA RP11 23J9.4 and X-ray have significant synergistic effect on TC. LncRNA RP11 23J9.4 can be used as a marker for TC targeted therapy.