直线加速器的连锁可分为主要连锁、次要连锁以及剂量连锁三大类。本文针对瓦里安C系列直线加速器的次要剂量 连锁UDR1、UDR2的故障，详细介绍此故障出现的原因以及如何快速排除。根据加速器的随机图纸以及射线产生的原理， 利用示波器、万用表等对相关指标进行检测，然后再对比结果与正常值的差异，对故障进行具体分析，最终通过更换继电 器K2及旁接AFC系统中的信号线解决故障。希望本文的维修思路分析，能为同行的维修提供参考借鉴。

The interlock of linear accelerators can be divided into three categories including primary interlock, secondary interlock, and dose interlock. This paper focused on the failure of secondary dose interlock UDR1 and UDR2 of the Varian C series linear accelerator, introduced in detail the causes of the failure and how to resolve it quickly. According to the random drawing of the accelerator and the principle of ray generation, the relevant indicators were detected by using oscilloscope and multimeter. Then, the difference between the results and the normal value were compared, and the fault was analyzed in detail. Finally, the fault was solved by replacing the relay K2 and the signal line in the side connected AFC system. We hope that the analysis of maintenance ideas can provide reference for peers.