Effects of compressive stress perpendicular to the surface of 4 percent silicon-iron single crystals on their magnetic properties were investigated. Picture frame single crystal specimens which were used had  and  orientation, respectively. The hysteresis loops at low field (0 < H <450 A/m) were measured under the applied stress. For the 4 percent Si-Fe  specimen, a large decrease of induction under stress occurs at lower fields, and for the 4 percent Si-Fe  specimen, the induction increases with increasing applied stress at lower fields but decreases at higher fields and coincides with the same value of the zero stress case when H is greater than about 400A/m. The stress versus Br/Bmcurves of the 4 percent Si-Fe  and  specimens were plotted to show the change of the induction under applied stress.