Objective: To explore the possible synergism of 100 Hz extremely low frequency magnetic field(ELF-MF) and X-ray in treatment of hepatoma-implanted Balb/c mice. Methods: Hepatoma-implanted mice were established using H22 cells. Magnetic flux 0.7 mT to 100 Hz ELF-MF was preparaed by spiral coil and 6 MV X-ray irradiation was generated by linear accelerator. Hepatoma-implanted mice were divided into 6 groups:control group,group of ELF-MF alone,group of 4 Gy X-ray treatment alone,group of 8 Gy X-ray treatment alone,group of 4 Gy X-ray combined with ELF-MF,group of 8 Gy X-ray combined with ELF-MF,each with 10. Tumor growth and survival of H22 cells-implanted mice were evaluated by measuring the tumor diameter every day and recording survival days. Furthermore,tumor growth and mice survival were examined when different times of ELF-MF exposures combined with 4 Gy X-ray.Data referring to overall survival days and tumor diameters of the above groups were compared using Log-rank test and Student's T test. Results: Compared with control group,X-ray alone could significantly reduce the tumor size and shorten the survival days. Moreover,the survival in the group of 8 Gy X-ray alone was significantly shorter than that of 4 Gy X-ray alone. Compared with group of ELF-MF alone or group of 4 Gy X-ray alone,4 Gy X-ray combined with ELF-MF could significantly extend the overall survival days and reduce the tumor size. Compared with group of 8 Gy X-ray alone,8 Gy X-ray combined with ELF-MF could significantly extend the overall survival days and reduce the tumor size; but compared with group of ELF-MF alone,the survival days of mice were significantly shortened. And more times of ELF-MF exposure could further improve the survival and inhibit tumor growth in hepatoma-implanted mice when combined with 4 Gy X-ray. Conclusions: ELF-MF could possibly synergize with 4 Gy X-ray in terms of survival improvement and tumor inhibition of hepatoma-implanted mice.