1. A depth determination method, comprising steps of: acquiring a color image and a depth image from a camera; performing image identification based on the color image, and determining a first image region of the color image where a feature object is recorded; determining a second image region of the depth image corresponding to the first image region in accordance with a correspondence between pixels of the color image and the depth image; and determining a feature depth of the feature object based on depth information corresponding to the pixels at the second image region, wherein the step of the determining the feature depth of the feature object based on the depth information corresponding to the pixels at the second image region comprises: acquiring an pixel depth of each pixel at the second image region of the depth image, thereby obtaining an pixel depth set; and determining the most frequently occurred pixel depth in the pixel depth set as the feature depth.