Objective　To synthesize and label a tumor positive imaging agent 18F-fluorouracil (FU) and the animal study on the product was also undertaken. Methods　18F-FU was synthesized and labeled. Its biodistribution analysis was done on normal and tumor bearing nude mice. PET imaging was performed on normal and tumor bearing rabbits. Results　HPLC analysis and other quality control test results guaranteed the possibility of animal study and clinical usage of 18F-FU. Biodistribution analysis and PET imaging also demonstrated a high accumulation of the tracer in tumor tissue. Conclusion　18F-FU is a kind of potential tumor positive imaging agents which can be used to assess the effects of chemotherapy.