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在中国计量科学研究院25 MV医用加速器机架的0°和90°方向，分别用两套水箱开展了医用加速器等中心性能的剂量学实验研究。在水深100 mm处，用空腔电离室测量了6 MV光子的电离电流信号。对水箱定位、电离室定位因素引起的空腔电离室测量结果的不确定度进行了分析。结合现行的国家标准所允许的医用加速器的等中心误差，得到了相对等中心位置处的剂量学测量误差范围是－0．3％～＋0．5％。作为一个相对独立的方法，本工作可以为检验医用加速器等中心性能提供参考。“,”The study for the isocenter property of the clinical accelerator was performed via a dosimetric experi-ment on the 25 MV clinical accelerator in National Institute of Metrology, China.The experiment was carried out with two water phantoms at the gantry angle of 0 and 90 ,respectively.The ionizing current of 6 MV photon beam in a cavity chamber was measured at the water depth of 100 mm.The experimental uncertainties due to the positioning for the cavity chamber and the water phantom were analyzed.The divergence of the dosimetric measurement was evaluated in the range from -0.3%to 0.5%with respect to the isocenter position, accord-ing to the allowed deviation of the isocenter suggested by the current national standard.As a separate way, the method proposed in this work can be used to quantitatively verify the isocenter property of the clinical accelera-tor.