When selecting the ventilation mode of small distribution, usually because of the cost considerations and underestimate of the demand of ventilation and heat dissipation, simply natural ventilation to dissipate heat is adopted. Thus, the wastage of the equipments is increased, the efficiency is reduced, the life span is shortened, and even the equipments are forced to stop. Taking Z mine substation ventilation reform design as an example, the choice of the ventilation mode of small substation was analyzed in details and pertinence, and on the basis of scheme comparison, some corresponding optimized suggestions were proposed on the ventilation design works.