用解析的方法研究了同向和反向运动束流激发的纵向尾场，并且给出了线性近似下束团 沿环不均匀分布情形下的双束流多束团纵向不稳定性的计算公式，得出了双束流不稳定性与高频腔（或 其它类腔结构）在环上位置及模的对称性有关的结论。 The longitudinal tail-fields excited by the same-direction and opposite-direction beam currents are studied analytically, and the formulas for calculating the longitudinal instability of a multi-bundle with two beams are given under the linear approximation. , We conclude that the instability of the two-beam flow is related to the position of the high-frequency cavity (or other cavity-like structure) on the ring and the symmetry of the mode.