Through the explosion and dynamic strain measurement of three models for several times, an expression of peak strain of main blasthole with different media and decouple coefficients and a semi-experienced calculation method of dynamic stress in explossion were obtained, and another method for the calculation of pre-splitting blasting parameters and smooth blasting parameters was put forward. The measured pre-splitting seams can reduce 23.6% ~ 60% of the peak strain of main blasthole