The invention discloses a measurement method of underwater bending-torsion shape and location of a fuel assembly after irradiation. The method comprises the steps that a standard distance on a locating grid is taken; collimating plumb lines are fixed on the edge of the locating grid of the fuel assembly; a vidicon is moved to perform video recording acquisition; a pixel value in video recording is read and fitted with pixel values between two adjacent longitudinal slits on the locating grid to obtain bending; a scale label value and a corresponding pixel value on a display screen are read; a pixel value and angle value relation curve is fitted; a pixel value of a distance from the edge of the locating grid to the superposed plumb lines when the two plumb lines are superposed in the video recording is read; the vidicon is moved to finish the video recording to obtain torsion of a lower pipe base relative to an upper pipe base. The method is convenient to operate, and can realize rapid non-contact measurement of the bending and the torsion of the fuel assembly in first time after the irradiation; scale calibration is adopted, so that an apparent error of a video image is reduced; the measurement accuracy is improved; longitudinal continuous measurement of the fuel assembly can be realized; the measurement efficiency is improved.