On the west line of southtonorth water diversion project, the total length of water diversion tunnels is 325.6km; the longest tunnel is 73km; the maximum tunnel diameter is 12m; the average tunnel depth is 500 m; the maximum depth is 1150m; the elevation in construction areas is 3500 to 4500m. Based on the technologies of the ventilation in tunnel’s construction in China, in combination with the deep long tunnel’s construction and design on the west line, a preliminary study on the ventilation length, ventilation mode, ventilation parameters, equipment selection, and ventilation layout etc in the onedirection excavation tunnels bored by TBM is presented in this paper.