Abstract: In this paper, the process of deformation in combined extrusion is expounded. Using the ideal plastic-rigid material model, according to different boundary condition, the slip-line fields of deformational zone during combined extrusion are established. And then, starting from known boundary conditions for the stresses, the stess fields of plastic zone and the distribntve law of normal stress on the end face of the punch are found out. On these grounds, the loading in combined extrusion is calculclated. The calculated values have been verified through experiments. Compared with actual values, their error is not more than five per cent. In addition, this paper analyses and discusses the value relationship among the peak loads of forward extrusion, dackward extrusion and combined extrusion under various rates of deformation and with or without cut-off. In order to reasonably determine the loading in combined extrusion, sevral views are presented. Thus, the problem of engineerig calculation of the loading in combined extrusion can be solved simply and accurately dy means of usual nomogram.