Abstract: Reasonable ventilation design is significant to reduce the risk of serious gas disaster when a tunnel pass? es through the coal measure strata with a long distance. Aiming at the ventilation problem of the of Laofangzi tunnel on Chengdu-Guiyang high-speed railway passing through gas-rich stratum, a six-stage ventilation scheme with forced ventilation at the first and second stage and gallery ventilation at the later stages, which can be adjusted with the construction progress, is designed. The simulation analysis is conducted by Fluent software, and it is verified with practical measured results. The results show the effect of the fourth stage ventilation is the poorest and most unfavorable condition; the gas concentration during the fourth stage ventilation is smaller than the threshold of 0.5 % and the max. gas concentration during the other ventilation stages is 0.08 %, meeting the requirements of specification. It can be seen that the effect of six-stage ventilation scheme is positive.