A 3D depth image acquiring method, wherein the method is applicable to an image acquisition device comprising a visible light-infrared light (VIS-NIR) picture sensor and an infrared structured light projection component, the VIS-NIR picture sensor comprising a plurality of dot matrix units, and a blue light photosensitive component, a green light photosensitive component, a red light photosensitive component, and an NIR photosensitive component being distributed on each of the dot matrix units, wherein the method comprises steps of: controlling the NIR photosensitive component and the infrared structured light projection component to operate, so as to obtain a plurality of NIR images, and obtaining an optimum NIR image from the plurality of NIR images; controlling the blue light photosensitive component, the green light photosensitive component, and the red light photosensitive component to operate, so as to obtain a plurality of VIS images, and obtaining an optimum VIS image from the plurality of VIS images; performing calculation on the optimum NIR image by using a 3D depth mode to obtain a depth image; and processing the depth image and the optimum VIS image to obtain a 3D depth image; characterized in that the image acquisition device further comprises a focusing motor and a lens, and the step of controlling the NIR photosensitive component and the infrared structured light projection component to operate so as to obtain a plurality of NIR images and obtaining an optimum NIR image from the plurality of NIR images comprises: controlling the NIR photosensitive component and the infrared structured light projection component to operate; and simultaneously adjusting a distance between the VIS-NIR picture sensor and the lens by controlling a position of the focusing motor to obtain the plurality of NIR images at different focal lengths; and selecting the optimum NIR image from the plurality of NIR images. a visible light-infrared light (VIS-NIR) picture sensor and an infrared structured light projection component, the VIS-NIR picture sensor comprising a plurality of dot matrix units, and a blue light photosensitive component, a green light photosensitive component, a red light photosensitive component, and an NIR photosensitive component being distributed on each of the dot matrix units, a plurality of dot matrix units, and a blue light photosensitive component, a green light photosensitive component, a red light photosensitive component, and an NIR photosensitive component being distributed on each of the dot matrix units, controlling the NIR photosensitive component and the infrared structured light projection component to operate, so as to obtain a plurality of NIR images, and obtaining an optimum NIR image from the plurality of NIR images; controlling the blue light photosensitive component, the green light photosensitive component, and the red light photosensitive component to operate, so as to obtain a plurality of VIS images, and obtaining an optimum VIS image from the plurality of VIS images; performing calculation on the optimum NIR image by using a 3D depth mode to obtain a depth image; and processing the depth image and the optimum VIS image to obtain a 3D depth image; characterized in that the image acquisition device further comprises a focusing motor and a lens, and a focusing motor and a lens, and the step of controlling the NIR photosensitive component and the infrared structured light projection component to operate so as to obtain a plurality of NIR images and obtaining an optimum NIR image from the plurality of NIR images comprises: controlling the NIR photosensitive component and the infrared structured light projection component to operate; and simultaneously adjusting a distance between the VIS-NIR picture sensor and the lens by controlling a position of the focusing motor to obtain the plurality of NIR images at different focal lengths; and selecting the optimum NIR image from the plurality of NIR images. controlling the NIR photosensitive component and the infrared structured light projection component to operate; and simultaneously adjusting a distance between the VIS-NIR picture sensor and the lens by controlling a position of the focusing motor to obtain the plurality of NIR images at different focal lengths; and selecting the optimum NIR image from the plurality of NIR images.