An electronic-component assembly system is provided in the invention. The electronic-component assembly system includes a gripping device, a light-source device, a photographing device, and an image-processing device. The gripping device grips an electronic component, wherein the electronic component includes at least one pin. The light-source device includes a light source and emits light of the light source. The photographing device senses the light and generates a plurality of first one-dimensional images corresponding to the pins at different rotation angles. The image-processing device is coupled to the photographing device to receive the plurality of first one-dimensional images. The image-processing device transforms the plurality of first one-dimensional images into a two-dimensional image, generates adjustment information according to the two-dimensional image, and provides adjustment information to the gripping device, wherein the gripping device adjusts the angle and position of the electronic component according to the adjustment information.