Abstract: As a profile control blasting technology, smooth blasting is widely used in conservancy engineering construction. The diameter of holes, the distance between them, the density of explosive filling medicine and the decoupling coefficient are the important factors affecting blasting quality. Based on the adiabatic equation, the formulas of decoupling coefficient are deduced and practised in typical engineering to obtain the value range of axial decoupling coefficient, and the axial decoupling coefficient under different radial decoupling coefficient is calculated.A curve indicating the relationship between the two coefficients is drawn to give reference for the value of them in similar projects.