Abstract: According to the pressure balanced system of the fire prevention and control hard to ensure the stable pressure balanced effect in the pressure balance d area, the paper had a study on the pressure balanced system with the local fan-air window adjustment for fire prevention and control.The study showed that the press ure balanced system for fire prevention and control mainly affected by the natural ventilation pressure, frictional ventilation resistance, sealing condition of the coal mini ng face, air content within the goaf, fire and ventilation pressure and fire tendency development.With the qualitative analysis of each influence factor, the inner and oute r pressure difference function of the goaf with time variation was obtained.The adjustment method of the pressure balanced system was summarized.When the inner an d outer pressure difference of the goaf was more than a certain value, the ventilation leakage of goaf would have high influences to the spontaneous combustion of the coal left in goaf.The pressure balanced system should be adjusted to reduce the inner and outer pressure difference of goaf.Finally the method was successfully applie d to open the sealing of No.6-201 fully mechanized top coal caving mining face in Laiyegou Mine.