Abstract: A novel polyoxometalate containing 5-fluorouracil with Keggin structure C₄H₄FN₂O₂H₂PW₁₂O₄₀·8H₂O was synthesized and structurally characterized by elemental analysis, IR spectra, UV spectra, X-ray powder diffraction, ¹⁸³W NMR and TG. The results of IR, UV and XRD indicted that the compound has Keggin and ring structures of 5-fluorouracil. It is shown that tungsten atoms of the compound are in the same chemical environment by the ¹⁸³W NMR spectra of the compound. The result of TG showed that the compound has good thermal stability, and the weightlessness has two steps. In human renal embryonic cell HEK293 with 5-fluorouracil for the positive control group, the ivtro cytotoxicity test of the compound was studied by MTT method. The TC₅₀ of the compound is 1.48×10^–5 mol· L^–1 and its toxicity is lower than 5-fluorouracil.