The frequence and modal of main stream piping were analysed under the condition of different velocity of stream and the valve taken as the centralizing mass . this paper also gives the responses of steady state under the condition that the frequency of forced vibration is 4hz 、 8hz 、 12hz respectively 将阀门作为集中质量处理，分析计算不同蒸汽流速下，某汽轮机主蒸汽管道系统的振动频率和振型，并给出了激振力频率分别为4hz 、 8hz 、 12hz时该管道系统的稳态响应。
