本文提出以双聚焦、无空间色散的设计原则,来代替常用的全消色差设计原则,使医用电子直线加速器的偏转磁铁能够具有更好的特性。为实用需要,探讨了缩短靶与磁铁出口的距离和改变入射角所引起的影响,以便减少旋转治疗头的回转半径和设计更轻巧的偏转磁铁。 In this paper, the design principle of double focusing and no space dispersion is proposed to replace the commonly used full achromatic design principle, which can make the deflection magnet of medical linear accelerator to have better characteristics. For practical purposes, the effect of reducing the distance between the target and the exit of the magnet and changing the angle of incidence is discussed in order to reduce the radius of gyration of the rotary therapy head and to design a more compact deflection magnet.