In this paper a newly develoed helical coordinates is used to make out the solution of electromagnetic fields in the helix gap and calculate dispersion characteristics of tape helix slow wave structure for the first time . strict boundary conditions for magnetic fields are adopted and are treated rigorously by fourier expansion . besides , the radial propagation constant of every layer in the dielectric - loaded region is differentiated . some of practical tape helix slow wave structures have been calculated for dispersion characteristics and the calculated values accord with measured values very well . the authors also compare the calculated results with experiments for different structures by changing tape thickness or other structure parameters and find that the theory in the paper is universal 本文首次运用螺旋坐标系给出了带状螺旋线缝隙内的电磁场解，并据此计算了带状螺旋慢波结构的色散特性.文中采用了严格的边界条件，并以傅立叶展开进行了严格的数学处理.另外还首次对有介质区域内各层的径向传输系数作了区别.本文使用这种方法计算了我们已研制的一些宽带高功率行波管所用的慢波线结构的色散特性，理论与实验符合得很好.我们还计算了不同结构参数对色散特性的影响，并与实验作了对照，发现本文的理论有一定的普适性
