Abstract: A standing wave electron linear accelerating apparatus and a method thereof are disclosed. The apparatus comprises an electron gun configured to generate electron beams; a pulse power source configured to provide a primary pulse power signal; a power divider coupled downstream from the pulse power source and configured to divide the primary pulse power signal outputted from the pulse power source into a first pulse power signal and a second pulse power signal; a first accelerating tube configured to accelerating the electron beams with the first pulse power signal; a second accelerating tube configured to accelerate the electron beams with the second pulse power signal; a phase shifter configured to continuously adjust a phase difference between the first pulse power signal and the second pulse power signal so as to generate accelerated electron beams with continuously adjustable energy at output of the second accelerating tube.