螺旋波纹波导回旋行波管与采用圆波导的回旋行波管相比，有较大的带宽。介绍了它的线性注波互作用理论，并用该理论计算了不同的磁场与波导表面微扰幅度对Ka波段螺旋波纹波导回旋行波管线性增益的影响。计算结果与已报道的实验结果基本符合，说明该理论可以初步确定螺旋波纹波导回旋行波管的各项参数。

Gyrotron traveling-wave tube (gyro-TWT) with helical waveguide has wider instantaneous frequency bandwidth than that with smooth waveguide. This paper introduces the linear theory of its beam-wave interaction, and calculates the influence on linear gain of Ka-band gyro-TWT caused by changing the applied magnetic field and the amplitude of the groove. The results accord with those reported, indicating that the theory can be used to preliminarily determine the parameters of gyro-TWT assembly.