The variation of beam waist position, beam width and light power with injection current in GaAs-AlXGa1-XAs DH stripe-geometry lasers, and the relationship between the station-ary stability and transient self-sustained pulsation have been studied experimentally. When the injection current varies, the position of the vertical beam waist for all types of lasers is always at the laser facet, the vertical beam width remains unchanged. No matter whether or not there are changes in the horizontal beam waist position, the transient self-sustained pulsation usually appears when the horizontal width of the beam waist varies considerably, and the current range for which self-sustained pulsation occurs usually lies between A, B kinks in the light power characteristics.