Preparation method of HfF4 for Accelerator mass spectrometry(AMS) was studied. The HfO2 sample was transformed to HfF4 suited to AMS measurement through the purification flow and HfF4 preparation flow of HfF4.The decontamination coefficient of the purification flow is high
especially for tungsten. The sample is suitable to the measurement of AMS.The yield of the whole flow was about 70% for Hf. The decontamination coefficient for W was about 106.