Background: Radon protection is particularly important in underground uranium mining

and the migration regularity of radon and radon ventilation reliability are the base to solve the problem. Therefore

it is of practical significance to study the reliability of ventilation of uranium and radon migration. Purpose: The aim is to explore the radon diffusion regularity of seepage in porous media with system reliability and mechanism of radon exhalation. Methods: The exhalation and distribution of radon in the tunnel under the steady state and unsteady state were analyzed and the numerical simulation of the tunnel for radon migration was developed using MATLAB PDE toolbox. Results: Radon concentration within the tunnel increased with the length of flowing under both unstable and stable conditions with a period of time of ventilation. Calculation of reliability of tunnel based on the mechanism of radon exhalation reflected the exhalation and distribution of radon concentration of tunnel well. Conclusion: The results show that the understanding of the law on the radon exhalation provides reference for radon-prevention in underground space and ventilation and safe operation of uranium mine.Cited