The effects of different load waveforms on stress corrosion cracking (SCC) of X70 pipeline steel were studied by means of fluctuating slow strain rate tensile test (F-SSRT). The results show that the SCC sensitivity of F-SSRT specimens with square wave loading is weak, and the fracture is straight; the SCC sensitivity of F-SSRT specimens with superimposed triangular wave loading is in the middle, and the fracture edge is serrated; The F-SSRT specimens with superimposed sine wave loading own the strongest SCC sensitivity, and the fracture is an oblique section fracture extending along the 45° direction. Different superimposed loads with different waveforms result in different SCC test results including different fracture morphology and change rules, which are caused by the change of the direction and magnitude of the applied force of the superimposed load, not only attributing to the different superimposed load energy.