Abstract:The spherical and cylindrical dynamite sources as well as the concentrated-farce saurces including weight drop,vibrator and shocking force are researched by using explosion mechanics and theoretical mechanics. The researches give sourcefunctions,relevant analytic and numerical results of the incident field in seismic diffraction tomography. By using elastoplastic theory,impulse theorem and Laplace transform,displacement Green`s function is derived,and the convolution of Green`s function with source function is made then. In addition,the expression of displacement incident field and the corresponding graphic representations are offered finally。