For giving some references to improve radiation condition of dummy driving drift in underground uranium mines, this paper expounds the mathematical description of radon concentration and potential alpha energy of its progeny in ventilation airflow, and educes the calculation formula of the maximal driving length of dummy driving drift for exhausting radon and its progeny. Then, this paper studies the relationships between the maximal driving length (L(max)) and air-quantity of ventilation system for dummy driving drift (Q), section area of dummy driving drift (S), radon concentration of intake...