为明确高海拔特长隧道独头压入式通风极限距离条件下隧道内污染物的运移规律，以米拉山特长隧道为研究对象，采用数值模拟软件Fluent对独头压入式通风极限距离下的CO、粉尘等污染物运移规律进行研究，并结合现场实测数据进行验证分析。研究结果表明： 1）掌子面的粉尘质量浓度随通风时间呈现出先增后减的趋势，台车靠近掌子一侧存在粉尘聚集现象，其两侧的粉尘质量浓度值差异明显，但通风过程中台车区域粉尘质量浓度变化幅度不大； 2）工人呼吸面处粉尘质量浓度呈现明显的阶段性下降趋势，CO质量浓度则是线性增加到达峰值后，以二次函数的形式降低，CO质量浓度达标时间明显小于粉尘质量浓度达标时间； 3）工作区CO质量浓度呈二次函数变化，距离掌子面越远，气体质量浓度峰值越低，而粉尘质量浓度则是先增后减，最后趋于稳定，现场工作区施工时间应以粉尘质量浓度达标时间为准； 4）粉尘扩散距离与通风时间满足三次函数关系，CO气体扩散距离与通风时间呈线性关系。

To clarify the migration law of pollutants under the limit distance of deadend pressin ventilation mode in an extralong highaltitude tunnel, the Milashan tunnel is taken as the research object to conduct migration law study on CO and dust under the limit distance of deadend pressin ventilation using the numerical simulation software Fluent. Moreover, the site monitoring data are analyzed. The results show the following: (1) The dust concentration on the tunneling surface increases first and then decreases with the ventilation time. The dust concentrates at the trolley close to tunneling face, and the dust concentration in the trolley area varies little during ventilation. (2) The dust concentration at the breathing surface of workers decreases step by step, whereas the CO concentration increases linearly to the peak, and then decreases in the form of a quadratic function. The time for CO concentration reaching the control standard is less than dust. (3) The CO concentration in the working area shows a quadratic function variation mode. The CO concentration lowers as the distance from tunneling face increases, whereas the dust increases first and then decreases to a stable value. Accordingly, the working time should be referenced from the time for dust concentration reaching the control standard. (4) The relationship between the dust diffusion distance and ventilation time shows cubic function, whereas the relationship between CO diffusion distance and ventilation time is linear.