Multiple toxic gases, such as carbon monoxide (CO), are generated after blasting of plateau tunnel. To investigate the migration patterns of CO during the ventilation process following blasting in high-altitude tunnels, this paper employs a three-dimensional model of tunnel blasting excavation under push ventilation. The study utilizes computational fluid dynamics to explore the temporal and spatial evolution characteristics of CO under various operational conditions. The influence of relevant factors was quantified using the grey relational analysis method. Numerical simulations were then used to derive distribution functions for CO concentration in relation to altitude, ventilation time, and other factors. The results indicate that under the influence of push ventilation, multiple vortex regions form due to the interaction between ventilation jets and several recirculation areas, where the airflow velocity is slower and CO concentrations are higher compared to other nearby regions. The grey relational analysis method yielded correlation factors of 0.634039, 0.6572, and 0.6560 for altitude (H), distance from duct outlet to working face (L