We have synthesized the LiYF4:Ce3+ nanoparticles – Methotrexate (MTX), targeting pancreatic cancer cells via folate receptors. Under ultralow 0.1 Gy X-ray irradiation (the lowest dose in the world, for 2-3 times), the nanoparticles can exhibit radiosensitization effect,radiosensitizing chemotherapy, because of MTX released by X-ray inducing photocleavage of NPA linker. The dual sensitization effect will enhance ROS production, DNA damage, cell cycle S phase arrest in pancreatic cancer cells. We have also demonstrated the excellent efficacy in AsPC-1PANC-1 xenografted pancreatic mice.