The analysis of influence of the strain-stress condition on longitudinal splits formation in the extruded pipes from aluminum alloy АМg6 is made. The mechanism of heterogeneity of distribution of deformation at pressing-out of ingot is described by finite-element method. The same method is used for calculation of level of tangential pressure at level of a calibrating girder of a matrix. It is revealed that in the specified place there are the tension stresses resulting to destruction of metal. The results of experiment confirming presence of pressure are resulted. The conclusion is drawn on presence of the factors resulting to longitudinal splits formation.