Through the theoretical analysis,simulation test and coinmercial-scale trial,the results have shown that the air space can decrease the blasting pressure peak and ex-tend the time of blasting action,By adjusting the length of air space, the blasting actioncontrol and the blasting effect can be improved. It has been proved that there is an optimalrange of air space. And this optimai range was uesd for the adjustment of air space lengthin the large-diameter longhole mining in Tonglushan mine.