A computer-implemented method for adjusting backlight in measurement of a profile image of an object includes setting a light source of an image measuring machine to an original intensity level, obtaining the profile image of the object laid on the image measuring machine, and performing a mean filter processing and a binary image processing on the profile image. The method further includes setting intensity variables to adjust backlight intensity of the light source, uses the intensity variables to calculate an optimum intensity level of the backlight intensity utilizing an iterative method, and adjusting the backlight intensity of the light source to the optimum intensity level to obtain an optimum profile image of the object.