Heading face is a special underground workspace,  generally forced ventilation is chose to supply fresh air,  and the air movements in it belong to restricted wall-attached jet.  According to the characteristics of workspace in heading face,  this paper gives the definition of partial air age and average air age,  and their models for calculating.  Tracer gas method was used to menstruate the average air age,  and numerical simulation has been used to calculate the ventilation airfield of restricted wall-attached jet and average air age of heading face,  and elicit ventilation flow field and distributing of average air age of heading face.  Based on them,  relations between the air age and ventilation flow field,  ventilation validity are analyzed,  and the mathematical model of air exchange efficiency and ventilation efficiency of heading face were set up.  The study revealed that the major influences to air age are air-flow organization and blast volume,  and to air quality are air age and pollutant concentration.  The conclusion of this research provides a kind of new theory basis for appraising the ventilation validity of heading face.