The process of forming of Self Forging Fragment (SFF for short) is a very complicated problem of explosion. Because of SFF is axisymmetric, 2-d imentional elastic-plastic mechnical equations are used to discribe this process. In solving these equations, we use integral definitions of the partial derivatives by M.L. Wilkins,and Lagrange quadrilateral grid.The shape of the SFF obtained from our 2-dimensional numerical simulation compares fairly with that in the high speed x-ray photogragh of the actural experimental process.